Power compensation device for railway

Abstract

To provide a power compensation device for railways capable of further efficiently suppressing variations of a three-phase voltage.SOLUTION: A power compensation device for railways comprises a first single-phase converter, a second single-phase converter, a first acquisition section, a second acquisition section, and a command value calculation section. The first single-phase converter is connected to a first single-phase power side of a transformer, which converts three-phase power into first and second single-phase power, via a first feeder. The second single-phase converter is connected to a second single-phase power side of the transformer via a second feeder to which a larger load than the first feeder is connected. Based on 1 / 2 of a differential between a value obtained by adding a predetermined offset power value to a first effective power value and a second effective power value, the command value calculation section calculates a first effective power command value for the first single-phase converter and a second effective power command value for the second single-phase converter.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a railway power compensation device installed in an AC power feeding system. [Background technology]

[0002] The railway power compensation device described in Patent Document 1 is connected to the two-phase side of a three-phase / two-phase transformer that receives power from a three-phase AC power source in an AC power feeding system for a Shinkansen or the like, and interchanges and equalizes active power when a difference occurs in active power between the M phase and the T phase on the two-phase side. Furthermore, the railway power compensation device compensates for the reactive power of each of the M phase and the T phase in accordance with the difference between the actual voltage value and the target voltage value of the feeder lines of each of the M phase and the T phase. As a result, the railway power compensation device suppresses fluctuations in the three-phase voltage of the three-phase AC power source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-137966 A Summary of the Invention [Problem to be solved by the invention]

[0004] If the three-phase voltage of a three-phase AC power supply fluctuates significantly, it may affect other consumers connected to the same power system. Therefore, it is required to suppress the fluctuation range of the three-phase voltage within a controlled value. In the above-mentioned railway power compensation device, when the load on the two-phase side suddenly increases or decreases and exceeds the capacity of the device, the fluctuation range of the three-phase voltage may exceed the required control value.

[0005] The present disclosure provides a railway power compensation device capable of more efficiently suppressing fluctuations in three-phase voltage. [Means for solving the problem]

[0006] The power compensation device for railways according to the present disclosure includes a first single-phase converter, a second single-phase converter, a first acquisition unit, a second acquisition unit, and a command value calculation unit. The first single-phase converter is connected via a first feeder line to the first single-phase power side of a transformer that converts three-phase power into first and second single-phase powers. The second single-phase converter is connected via a second feeder line, to which a load larger than that of the first feeder line is connected, to the second single-phase power side of the transformer. The first acquisition unit acquires a first active power value based on a detected value of the active power or active current supplied to the first feeder line. The second acquisition unit acquires a second active power value based on a detected value of the active power or active current supplied to the second feeder line. The command value calculation unit calculates a first active power command value for the first single-phase converter and a second active power command value for the second single-phase converter based on one-half of the difference between the value obtained by adding a predetermined offset power value to the first active power value and the second active power value acquired by the second acquisition unit.

[0007] According to the power compensation device for railways of the present disclosure, an offset power value is added to the active power value on the second single-phase side where the load is smaller than that on the first single-phase side. As a result, the suppression range, which is the range of loads for which voltage fluctuations can be suppressed by the power compensation device, is shifted to the first single-phase side where the load fluctuations are large. Consequently, even if the load imbalance between the first single-phase side and the second single-phase side is within the suppression range, variations occur in the three-phase voltage, and the three-phase voltage when the load imbalance is within the suppression range approaches the three-phase voltage when the load imbalance is outside the suppression range. Therefore, even when the load on the single-phase side changes suddenly and the load imbalance changes from within the suppression range to outside the suppression range in a short period, the fluctuation range of the three-phase voltage is suppressed. Thus, the fluctuation of the three-phase voltage can be suppressed more efficiently.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0009] <1. Configuration of Railway Power System> Hereinafter, with reference to the drawings, the configuration of the railway power system 100 according to this embodiment will be described. As shown in FIG. 1, the railway power system 100 includes a three-phase AC power supply 10, a three-phase / two-phase transformer 20, a railway static power conditioner (hereinafter RPC) 30, an M-type catenary wire 41, a T-type catenary wire 42, an M-type voltage detection unit 11, a T-type voltage detection unit 12, an M-type power detection unit 21, and a T-type power detection unit 22.

[0010] The three-phase AC power supply 10 is a power supply of the upper system that receives power from the power company. The three-phase AC power supply 10 supplies three-phase AC power to the three-phase / two-phase transformer 20. The three-phase / two-phase transformer 20 is, for example, a Scott-connected transformer, which converts three-phase power into two sets of single-phase power with a 90° phase difference, namely, M-phase power and T-phase power. The M-phase wire 41 is connected to the M-phase two-phase side of the three-phase / two-phase transformer 20, and the M-phase power is supplied to the M-phase load via the M-phase wire 41. The T-phase wire 42 is connected to the T-phase two-phase side of the three-phase / two-phase transformer 20, and the T-phase power is supplied to the T-phase load via the T-phase wire 42. The M-phase load is a traction circuit load connected to the M-phase wire 41, and the T-phase load is a traction circuit load connected to the T-phase wire 42. The M-phase load and the T-phase load are, for example, railway vehicles.

[0011] The RPC 30 is connected to the M-phase wire 41 and the T-phase wire 42. In the railway power system 100, a load may concentrate on either the M-phase side or the T-phase side, resulting in an imbalance in the load between the M-phase and the T-phase. When the M-phase load and the T-phase load become unbalanced, a current containing a reverse-phase component flows into the three-phase AC power supply 10 of the upper system, and the three-phase voltage fluctuates more significantly than when the M-phase load and the T-phase load are equally large. When the three-phase voltage fluctuates significantly, it may affect other consumers connected to the three-phase AC power supply 10. Therefore, the power company supplying the three-phase AC power supply 10 is required to suppress the fluctuation range of the three-phase voltage within a management value (for example, 2% in two minutes).

[0012] To meet the above requirements, the RPC 30 transfers active power between the M-phase and the T-phase to suppress the imbalance in active power between the M-phase and the T-phase. In addition, the RPC 30 independently outputs reactive power that cancels out the reactive power of each of the M-phase load and the T-phase load for each of the T-phase and the M-phase, aiming to improve the power factor and maintain the voltage of the T-phase and the M-phase.

[0013] The M - seat voltage detection unit 11 detects the M - seat wire voltage value Vm of the M - seat wire 41 and outputs the M - seat wire voltage value to the RPC 30. The T - seat voltage detection unit 12 detects the T - seat wire voltage value Vt of the T - seat wire 42 and outputs the T - seat wire voltage value to the RPC 30. The M - seat power detection unit 21 detects the M - seat active power value Pm supplied to the M - seat wire 41 and outputs the M - seat active power value Pm to the RPC 30. The T - seat power detection unit 22 detects the T - seat active power value Pt supplied to the T - seat wire 42 and outputs the T - seat active power value Pt to the RPC 30. In another embodiment, the railway power system 100 may include an M - seat current detection unit and a T - seat current detection unit instead of the M - seat power detection unit 21 and the T - seat power detection unit 22. The M - seat current detection unit detects the M - seat active current value Im supplied to the M - seat wire 41 and outputs the M - seat active current value Im to the RPC 30. The T - seat current detection unit detects the T - seat active current value It supplied to the T - seat wire 42 and outputs the T - seat active current value It to the RPC 30.

[0014] <2. Configuration of RPC> The RPC 30 includes an M - seat transformer 31, a T - seat transformer 32, an M - seat inverter 33, a T - seat inverter 34, a DC circuit 35, and an arithmetic unit 50.

[0015] The M - seat transformer 31 is a single - phase transformer and is connected between the M - seat wire 41 and the M - seat inverter 33. The T - seat transformer 32 is a single - phase transformer and is connected between the T - seat wire 42 and the T - seat inverter 34.

[0016] The M - seat inverter 33 and the T - seat inverter 34 are single - phase self - excited inverters. The M - seat inverter 33 and the T - seat inverter 34 are connected to each other via the DC circuit 35 and transfer active power from one to the other via the DC circuit 35. The M - seat inverter 33 is controlled based on the M - seat active power command value Prefm and the M - seat reactive power command value Qrefm output from the arithmetic unit 50. The T - seat inverter 34 is controlled based on the T - seat active power command value Preft and the T - seat reactive power command value Qreft output from the arithmetic unit 50.

[0017] The arithmetic unit 50 is a processor including a CPU, a memory, etc. By executing a program stored in the memory by the CPU, various functions are realized. Part or all of the functions realized by the arithmetic unit 50 may be configured by a hardware logic circuit such as an LSI, an ASIC, or an FPGA.

[0018] The arithmetic unit 50 acquires the M-phase voltage value Vm, and calculates the M-phase reactive power command value Qrefm based on the difference between the M-phase voltage value Vm and the M-phase voltage command value so that the M-phase voltage value Vm follows the M-phase voltage command value. Further, the arithmetic unit 50 acquires the T-phase voltage value Vt, and calculates the T-phase reactive power command value Qreft based on the difference between the T-phase voltage value Vt and the T-phase voltage command value so that the T-phase voltage value Vt follows the T-phase voltage command value. Thereby, the voltage is easily maintained, and fluctuations in the three-phase voltage can be effectively suppressed.

[0019] Furthermore, the arithmetic unit 50 acquires the M-phase active power value Pm and the T-phase active power value Pt from the M-phase power detection unit 21 and the T-phase power detection unit 22, and calculates the M-phase active power command value Prefm and the T-phase active power command value Preft based on the difference between the M-phase active power value Pm and the T-phase active power value Pt. In another embodiment, the arithmetic unit 50 multiplies each of the M-phase active current value Im and the T-phase active current value It output from the M-phase current detection unit and the T-phase current detection unit by a predetermined voltage value to acquire the M-phase active power value Pm and the T-phase active power value Pt.

[0020] Based on the difference between the M-phase active power value Pm and the T-phase active power value Pt, active power is transferred from one of the M-phase and the T-phase to the other, thereby suppressing fluctuations in the three-phase voltage. The magnitude of the active power that can be transferred between the M-phase and the T-phase is determined by the capacity of the RPC30 (specifically, the capacities of the M-phase inverter 33 and the T-phase inverter 34).

[0021] When the active power to be transferred is set to 1 / 2 of the difference between the M-phase active power value Pm and the T-phase active power value Pt, if the load imbalance between the M-phase load and the T-phase load is within the capacity of the RPC30, the active power output from the M-phase side of the three-phase / two-phase transformer 20 and the active power output from the T-phase side are equalized. As a result, the inflow of the reverse-phase component current into the three-phase AC power supply 10 of the three-phase / two-phase transformer 20 is suppressed, so that the balance of the three-phase voltage is maintained and the fluctuation of the three-phase voltage is suppressed.

[0022] However, when the load imbalance exceeds the capacity of the RPC30, the active power on the M-phase side and the active power on the T-phase side of the three-phase / two-phase transformer 20 are not equalized, and an imbalance in the three-phase voltage occurs. Fig. 4 shows the M-phase equivalent load and the T-phase equivalent load on the three-phase side with respect to the difference obtained by subtracting the T-phase load (i.e., the T-phase active power value Pt) from the M-phase load (i.e., the M-phase active power value Pm) when the RPC according to the reference example is applied to the railway power system. The RPC according to the reference example sets the active power to be transferred to 1 / 2 of the difference between the M-phase active power value Pm and the T-phase active power value Pt. The RPC according to the reference example has a capacity of 40 MVA, and the suppression range is -40 MVA to 40 MVA. When the RPC according to the reference example is applied, when the load imbalance is within the range of -40 MVA to 40 MVA, the M-phase equivalent load and the T-phase equivalent load on the three-phase side are the same, but when the load imbalance is outside the range of -40 MVA to 40 MVA, the M-phase equivalent load and the T-phase equivalent load on the three-phase side are imbalanced.

[0023] Fig. 5 shows the change in the effective value of the three-phase voltage when the RPC according to the reference example is applied to the railway power system. When the M-phase load and the T-phase load are small and the load imbalance is within the suppression range of the RPC according to the reference example, the three-phase voltage is balanced. When the M-phase load or the T-phase load is large and the load imbalance is outside the suppression range of the RPC according to the reference example, the three-phase voltage is imbalanced. Therefore, when the M-phase load or the T-phase load changes suddenly and the load imbalance changes from within the suppression range to outside the suppression range of the RPC according to the reference example within a short period (e.g., within 2 minutes), the fluctuation range of the three-phase voltage may exceed the management value.

[0024] Here, when the load is biased towards either the M seat or the T seat, the load fluctuations will also be biased towards the side with the larger load. For example, when the M seat load is greater than the T seat load, the fluctuations in the M seat load will be larger than those in the T seat load. Therefore, in this embodiment, the arithmetic unit 50 shifts the suppression range of the RPC 30 towards the side with the larger M seat load and T seat load. That is, when the rated capacity of the RPC 30 is X, the arithmetic unit 50 shifts the suppression range from -X to X to -X + P_offset to X + P_offset. P_offset is the offset power. Which of the M seat load and the T seat load is larger is determined in advance.

[0025] For example, as shown in FIG. 2, when the M seat load is greater than the T seat load, the arithmetic unit 50 shifts the suppression range of the RPC 30 by 20 MVA towards the M seat side, and changes the suppression range of -40 MVA to 40 MVA to the suppression range of -20 MVA to 60 MVA. FIG. 2 shows the M seat equivalent load and the T seat equivalent load on the three-phase side with respect to the difference obtained by subtracting the T seat load from the M seat load when the RPC 30 with the offset power value P_offset set to 20 MVA is applied to the railway power system.

[0026] Even when the load imbalance is within the suppression range, there is a difference between the M seat equivalent load and the T seat equivalent load on the three-phase side by the amount of the offset power value P_offset. FIG. 3 shows the change in the effective value of the three-phase voltage when the RPC 30 is applied to the railway power system. Even when the M seat load and the T seat load are small and the load imbalance is within the suppression range of the RPC 30, the three-phase voltage is unbalanced. When the M seat load or the T seat load is large and the load imbalance is outside the suppression range of the RPC 30, the variation in the three-phase voltage is larger than when the load imbalance is within the suppression range of the RPC. However, since the degree of imbalance only changes significantly while the three-phase voltage is unbalanced, the variation range of the three-phase voltage is smaller compared to the case where the RPC according to the reference example is applied to the railway power system.

[0027] That is, in the present embodiment, when the load imbalance is within the suppression range of RPC30, the three-phase voltage is deliberately made unbalanced. As a result, even if the M-phase load or the T-phase load changes rapidly and the load imbalance goes out of the suppression range of RPC30 within a short period, the fluctuation range of the three-phase voltage is suppressed within the management value.

[0028] Specifically, as shown in FIG. 6, when the M-phase load is larger than the T-phase load, the arithmetic unit 50 calculates the M-phase active power command value Prefm and the T-phase active power command value Preft such that the active power, which is half of the difference between the value obtained by adding the offset power value P_offset to the T-phase active power value Pt and the M-phase active power value Pm, is transferred from the T-phase side to the M-phase side.

[0029] When the M-phase load is set to 10 MVA, the T-phase load is set to 0 MVA, and the offset power value P_offset is set to 20 MVA, 5 MVA of active power is transferred from the M-phase side to the T-phase side. Therefore, 5 MVA of active power is input to the two-phase T-phase side of the three-phase / two-phase transformer 20, and 15 MVA of active power is output from the two-phase M-phase side.

[0030] If the offset setting of RPC30 is always enabled, even when the two-phase side is unloaded, RPC30 is energized and power loss occurs as it attempts to transfer active power between the M-phase and the T-phase according to the offset power value P_offset. Therefore, as shown in FIG. 7, when the two-phase side is below the no-load determination value (for example, 2 MVA) and can be regarded as no-load, the offset setting is disabled, that is, the offset power value P_offset is set to zero. In this case, the two-phase side is no-load, and since the offset setting is disabled, RPC30 is not energized.

[0031] <2. Calculation of M-phase and T-phase active power command values> <2-1. First example of arithmetic unit> Next, referring to FIG. 8, as a first example of the arithmetic unit 50, the arithmetic unit 50 when the T-phase load is larger than the M-phase load will be described. The arithmetic unit 50 calculates an M-phase active power command value Prefm such that the input direction of the M-phase inverter 33 is positive and the output direction is negative, and calculates a T-phase active power command value Preft such that the input direction of the T-phase inverter 34 is positive and the output direction is negative.

[0032] The arithmetic unit 50 includes a determination unit 51, a delay unit 52, an offset output unit 53, a subtraction unit 54, an addition unit 55, a first gain unit 56, a second gain unit 57, a third gain unit 58, an M-phase active power limiter 61, and a T-phase active power limiter 62.

[0033] The determination unit 51 determines whether the T-phase active power value Pm is greater than the no-load determination value Pno. The no-load determination value Pno is a determination value for determining whether the T-phase load can be regarded as a no-load. Since the M-phase load is smaller than the T-phase load, if the T-phase load can be regarded as a no-load, the M-phase load can also be regarded as a no-load.

[0034] When the determination unit 51 determines that the T-phase active power value Pm is greater than the no-load determination value Pno, that is, when it determines that the two-phase side is not a no-load, it outputs "1" to the delay unit 52. When the determination unit 51 determines that the T-phase active power value Pm is less than or equal to the no-load determination value Pno, that is, when it determines that the two-phase side is a no-load, it outputs "0" to the delay unit 52.

[0035] When the input of "0" from the determination unit 51 continues for a predetermined time, the delay unit 52 outputs "0" to the offset output unit 53, and in other cases, it outputs "1" to the offset output unit 53.

[0036] When "1" is input from the delay unit 52, the offset output unit 53 outputs an offset power value P_offset greater than 0 to the addition unit 55. When "0" is input from the delay unit 52, the offset output unit 53 outputs "0" (i.e., the offset power value P_offset = 0) to the addition unit 55. Therefore, when it is determined that the T-phase active power value Pm is less than or equal to the no-load determination value P_no for a continuous predetermined time, the offset power value P_offset is set to zero, and the offset setting becomes invalid. Otherwise, the offset setting becomes valid.

[0037] If the offset setting of the RPC 30 is frequently switched between valid and invalid, that is, between an offset power value P_offset of zero and a value greater than zero, the three-phase voltage may oscillate, or the transient voltage fluctuation of the three-phase voltage may exceed the management value. Therefore, when it is determined that the T-phase active power value Pm is greater than the no-load determination value P_no for a continuous predetermined time, the offset power value P_offset is set to zero. The predetermined time is set to a time longer than the fluctuation range of the management value. For example, when the management value is 2% in 2 minutes, the predetermined time is set to 2 minutes and 10 seconds, which is longer than the 2-minute fluctuation range of the management value.

[0038] The subtraction unit 54 outputs the difference obtained by subtracting the T-phase active power value Pt from the M-phase active power value Pm to the addition unit 55. The addition unit 55 outputs the added value obtained by adding the output of the subtraction unit 54 and the output of the offset output unit 53 to each of the first gain unit 56 and the third gain unit 58. The added value is the M-phase active power value Pm + the offset power value P_offset - the T-phase active power value Pt. That is, the added value corresponds to the difference between the value obtained by adding the offset power value P_offset to the active power value of the phase with the smaller load between the M-phase and the T-phase and the active power value of the phase with the larger load.

[0039] The first gain unit 56 multiplies the output value of the addition unit 55 by a gain of "-1" and outputs it to the second gain unit 57. The second gain unit 57 multiplies the output value of the first gain unit 56 by a gain of "1 / 2" and outputs it to the M-plane active power limiter 61. The third gain unit 58 multiplies the output value of the addition unit 55 by a gain of "1 / 2" and outputs it to the T-plane active power limiter 62.

[0040] Based on the M-plane reactive power command value Qm, the M-plane active power limiter 61 limits the output value of the second gain unit 57 within a predetermined range so that the current input to the M-plane inverter 33 does not become an overcurrent, and outputs the M-plane active power command value Prefm to the M-plane inverter 33. Specifically, if the output value of the second gain unit 57 is within the predetermined range, the M-plane active power limiter 61 sets the output value as the M-plane active power command value Prefm. When the output value of the second gain unit 57 exceeds the upper limit value of the predetermined range, the upper limit value is set as the M-plane active power command value Prefm. When the output value of the second gain unit 57 is below the lower limit value of the predetermined range, the lower limit value is set as the M-plane active power command value Prefm. That is, the M-plane active power limiter 61 calculates the M-plane active power command value Prefm based on half of the output value of the addition unit 55 and outputs the M-plane active power command value Prefm to the M-plane inverter 33.

[0041] Similar to the M-plane active power limiter 61, based on the T-plane reactive power command value, the T-plane active power limiter 62 limits the output value of the third gain unit 58 within a predetermined range so that the current input to the T-plane inverter 34 does not become an overcurrent, and outputs it as the T-plane active power command value Preft to the T-plane inverter 34. That is, the T-plane active power limiter 62 calculates the T-plane active power command value Prefm based on half of the output value of the addition unit 55 and outputs the T-plane active power command value Prefm to the T-plane inverter 34.

[0042] <2-2. Second Example of the Arithmetic Unit> Next, referring to Fig. 9, a second example of the calculation unit will be described, in which the M-seat load by the calculation unit 50 is greater than the T-seat load. Here, differences from the first example of the calculation unit 50 will be described. The second example of the calculation unit 50 includes a fourth gain unit 59 in addition to the configuration of the first example of the calculation unit 50.

[0043] The fourth gain unit 59 is disposed between the offset output unit 53 and the adder unit 55. The fourth gain unit 59 multiplies the output value of the offset output unit 53 by "-1" and outputs the result to the adder unit 55. Therefore, the added value output from the adder unit 55 becomes the M-phase active power value Pm- (T-phase active power value Pt+offset power value Poffset). In other words, the added value corresponds to the difference between the active power value of the M-phase or T-phase with the smaller load added to the offset power value Poffset, and the active power value of the phase with the larger load.

[0044] <3.Effects> By setting an offset in the RPC 30, the suppression range of the RPC 30 is shifted to the one with the larger load, either the M or T switch. As a result, when the load imbalance of the M and T switches is within the suppression range of the RPC 30, the three-phase voltage becomes unbalanced and approaches the three-phase voltage when the load imbalance is outside the suppression range of the RPC 30. Therefore, even if the M switch load or the T switch load changes suddenly and the load imbalance goes from within the suppression range of the RPC 30 to outside the suppression range in a short period of time, the fluctuation range of the three-phase voltage is suppressed within the control value.

[0045] Therefore, by applying the RPC30 to a railway power system, it is possible to compensate for the reactive power of the M phase and the T phase while maximizing the negative-phase power suppression function by interchange of active power between the M phase and the T phase, thereby efficiently suppressing fluctuations in three-phase voltage.

[0046] In addition, when it is determined that the M load and the T load are unloaded, the offset power value Poffset is set to zero, thereby suppressing power loss due to current flow within the RPC 30 and achieving energy savings.

[0047] Furthermore, when it is determined that the M-phase load and the T-phase load are both unloaded for a continuous predetermined time, the offset power value Poffset is set to zero, thereby suppressing frequent switching between enabling and disabling the offset setting. As a result, it is possible to suppress the vibration of the three-phase voltage associated with frequent switching between enabling and disabling the offset setting, and the transient fluctuation of the three-phase voltage that exceeds the management value.

Explanation of Signs

[0048] 10…Three-phase AC power supply, 20…Three-phase / Two-phase transformer, 30…RPC, 33…M-phase inverter, 34…T-phase inverter, 35…DC circuit, 41…M-phase lead wire, 42…T-phase lead wire, 50…Arithmetic unit, 100…Railway power system.

Claims

1. A first single-phase converter connected via a first feeder wire to the first single-phase power side of a transformer that converts three-phase power into first and second single-phase powers; A second single-phase converter connected via a second feeder wire, to which a load larger than that of the first feeder wire is connected, to the second single-phase power side of the transformer; A first acquisition unit that acquires a first active power value based on a detected value of the active power or active current supplied to the first feeder wire; A second acquisition unit that acquires a second active power value based on a detected value of the active power or active current supplied to the second feeder wire; Based on one half of the difference between the value obtained by adding a predetermined offset power value to the first active power value and the second active power value acquired by the second acquisition unit, a first active power command value for the first single-phase converter and a second active power command value for the second single-phase converter are calculated, a command value calculation unit; comprising, A railway power compensation device.

2. The command value calculation unit determines whether the first active power value is less than or equal to a no-load determination value, and when it is determined that the first active power value is less than or equal to the no-load determination value, sets the offset power value to zero. The railway power compensation device according to Claim 1.

3. The command value calculation unit determines whether the first active power value has been less than or equal to the no-load determination value continuously for a predetermined time, and when it is determined that the first active power value has been less than or equal to the no-load determination value continuously for a predetermined time, sets the offset power value to zero. The railway power compensation device according to Claim 2.

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