Voltage regulator

Abstract

To provide a voltage regulator that efficiently detects abnormalities in a changeover switch.SOLUTION: A voltage regulator 100 includes series transformers 11, 12 having secondary windings 112, 122 connected in series to distribution lines 1u, 1v that distribute AC from a power source to a load, a regulating transformer 2 having a primary winding connected in parallel to the distribution line, and an on-load tap changer 3 having changeover switches Th1 to Th3, ThA to ThC for switching and selecting taps on the windings of the regulating transformer, and connecting selected taps t1 to t3 for winding 20 to output AC, and the on-load tap changer includes a control unit that turns the changeover switch on or off to switch the tap, and the control unit acquires a circuit voltage value of an on-load tap changer (OLTC) circuit 4 including the changeover switch and a secondary voltage value on the secondary side, and determines whether there is an abnormality in the changeover switch on the basis of the acquired circuit voltage value and secondary voltage value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a voltage regulator. [Background technology]

[0002] A voltage regulator using the so-called indirect switching method comprises a series transformer whose secondary winding is connected in series to the distribution line, a regulating transformer whose primary winding is connected in parallel to the distribution line and whose secondary winding has multiple taps, and a tap changer that switches the multiple taps to connect them to the primary winding of the series transformer.

[0003] A tap changer includes a changeover switch for changing the tap connected to the primary winding of the series transformer, a current limiting element such as a current limiting resistor that limits the fault current flowing between the taps during the tap changing process, and a fault correction switch that connects and disconnects the current limiting element between the taps. The current limiting resistor and fault correction switch are connected in series. The tap changer switches the magnitude and polarity of the regulated voltage applied from the regulating transformer to the primary winding of the series transformer by turning the changeover switch and the fault correction switch on and off in a predetermined sequence.

[0004] A switch such as an electromagnetic contactor having mechanical contacts is connected in parallel to the series circuit of the current-limiting resistor and the fault correction switch (see Patent Document 1). This switch is designed to close when the change-over switch becomes uncontrollable or when a large current flows through the tap changer due to a short circuit or other cause in the distribution line. In this case, a b-contact (normally closed contact) is used as the mechanical contact so that it closes in the event of a power loss. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-312612 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the switch disclosed in Patent Document 1 does not take into consideration the efficient determination of abnormality in the change-over switch.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a voltage regulator that can efficiently determine whether a change-over switch has an abnormality. [Means for solving the problem]

[0008] A voltage adjustment device according to one embodiment of the present disclosure is a voltage adjustment device including: a series transformer having a secondary winding connected in series to a distribution line that distributes alternating current from a power source to a load; a regulating transformer having a primary winding connected in parallel to the distribution line; and an on-load tap changer having a changeover switch for switching and selecting a tap on the winding of the regulating transformer, which connects the selected tap on the winding to output alternating current, wherein the on-load tap changer has a control unit that turns the changeover switch on or off to control the tap switching, and the control unit acquires a circuit voltage value of an OLTC circuit including the changeover switch, acquires a secondary-side voltage value on the secondary side, and determines whether there is an abnormality in the changeover switch based on the acquired circuit voltage value and secondary-side voltage value.

[0009] In this aspect, the voltage regulating device includes a series transformer, a regulating transformer, and an on-load tap changer. The on-load tap changer includes a changeover switch for switching and selecting a tap of the regulating transformer, and a control unit that controls the tap switching by turning the changeover switch on or off. The control unit is configured, for example, by a microcomputer including a storage unit such as a ROM or RAM. The storage unit further stores, in a table format (tap position table), tap positions determined by tap switching and values ​​related to the turns ratio of the regulating transformer at the tap positions. The changeover switch is configured, for example, by a semiconductor element such as a thyristor. Two changeover switches are connected to each tap of the regulating transformer, and these multiple changeover switches are connected in parallel to form an on-load tap changer (OLTC) circuit. In other words, the OLTC circuit includes the multiple changeover switches. The control unit acquires a primary-side voltage value indicating the voltage on the power source side connected to the voltage regulator and a secondary-side voltage value indicating the voltage on the load side connected to the voltage regulator. For example, if the power source is a single-phase power source, the distribution line may include a u-phase distribution line and a v-phase distribution line, and a measurement transformer may be provided between these distribution lines. The control unit acquires a reference voltage value stored in a memory unit such as a ROM. The reference voltage value is set in advance according to the device characteristics or specifications of the voltage regulator. The reference voltage value corresponds to the reference voltage value on the secondary side, i.e., the output side. The control unit adjusts the voltage of the secondary-side distribution line by switching the tap of the regulating transformer. The OLTC circuit is applied with a voltage selected by a changeover switch in the on-load tap changer (tap voltage corresponding to the tap position), and is provided with a measurement transformer (circuit measurement transformer) that detects the circuit voltage of the OLTC circuit (OLTC circuit voltage). The control unit determines whether any of the changeover switches (thyristors) included in the OLTC circuit is abnormal based on the voltage value (OLTC circuit voltage value) obtained from the measurement transformer of the OLTC circuit and the secondary side voltage value.For example, it is expected that an abnormality in the low-voltage distribution line, which is the secondary distribution line, will also cause a voltage abnormality in the OLTC circuit, and if an abnormality determination is made to determine whether or not the change-over switch (thyristor) has failed based solely on voltage detection of the OLTC circuit, i.e., solely on the circuit voltage value (OLTC circuit voltage value), there is a concern that the accuracy of the determination result will be affected.In response to this, the control unit determines whether or not the change-over switch has an abnormality based on the circuit voltage of the OLTC circuit (OLTC circuit voltage) and the secondary-side voltage value, thereby effectively eliminating the effects of disturbances such as voltage abnormalities in the low-voltage distribution line, improving the determination accuracy in determining whether or not the change-over switch has an abnormality and significantly reducing the possibility of erroneous determination.

[0010] In a voltage adjustment device according to one embodiment of the present disclosure, the control unit calculates a voltage ratio between the circuit voltage value and the secondary voltage value, and determines whether there is an abnormality in the changeover switch based on the result of comparing the calculated voltage ratio with a reference ratio corresponding to the current tap position.

[0011] In this embodiment, the control unit calculates the voltage ratio between the circuit voltage value (OLTC circuit voltage value) and the secondary voltage value, for example, by dividing the secondary voltage value by the circuit voltage (OLTC circuit voltage value) (secondary voltage value ÷ OLTC circuit voltage value). In this case, the control unit may calculate the voltage ratio by division (voltage ratio = secondary voltage value / OLTC circuit voltage value) if the tap position is other than a through tap, or by dividing the OLTC circuit voltage value by the secondary voltage value if the tap position is a through tap. The control unit may store, for example, the current tap position or the output state of control signals for multiple changeover switches (thyristors) included in the on-load tap changer in a memory unit such as a microcomputer, and acquire information about the current tap position by referring to the memory unit. Furthermore, the memory unit such as a microcomputer constituting the control unit defines an association between the tap positions and the reference ratios corresponding to each tap position. A tap position table is stored, and the control unit can identify the reference ratio corresponding to the current tap position by referring to the tap position table. The control unit then compares the voltage ratio, which indicates the ratio between the circuit voltage value (OLTC circuit voltage value) and the secondary voltage value, with a reference ratio corresponding to the current tap position, and determines whether the changeover switch (thyristor) has an abnormality based on this.In this way, by using the tap position table for the calculated voltage ratio between the circuit voltage and the secondary voltage value, the control unit can efficiently determine whether the changeover switch (thyristor) has an abnormality through relatively simple calculation processing.

[0012] In a voltage adjustment device according to one aspect of the present disclosure, the control unit determines that the changeover switch is normal if the voltage ratio is within a predetermined settling range relative to the reference ratio, and determines that the changeover switch is abnormal if the voltage ratio is outside the predetermined settling range relative to the reference ratio.

[0013] In this aspect, the control unit determines that the changeover switch is normal if the calculated voltage ratio is within a predetermined settling range for a reference ratio, and determines that the changeover switch is abnormal if the calculated voltage ratio is outside the settling range. The settling range for the reference ratio is stored in a memory unit, such as a microcomputer, that constitutes the control unit, and the control unit can acquire each reference ratio corresponding to each tap position by referring to the memory unit. By providing a settling range for the reference ratio in this way, robustness can be ensured when comparing the calculated voltage ratio with the reference ratio, and abnormality determination of the changeover switch (thyristor) can be efficiently performed using relatively simple calculation processing.

[0014] In a voltage regulator according to an aspect of the present disclosure, the settling range is predetermined to be within a range of ±10% of the reference ratio.

[0015] In this embodiment, the settling range is predetermined as a ±10% range of the reference ratio. This ±10% settling range may be applied when the tap position is not a through tap. If the reference ratios for each tap position are set in 1.0 intervals, such as 1.0, 2.0, and 3.0, setting the settling range to ±10% allows the reference ratio to be set in ranges of 0.9 to 1.1, 1.8 to 2.2, and 2.7 to 3.3, thereby eliminating the effects of errors or disturbances in voltage measurement. Alternatively, the settling range may be set within a ±5% range. The settling range may be variably set, for example, by receiving input from a maintenance technician of the voltage regulator device via a programmable logic controller (PLC) or control panel and storing the received settling range value in a memory unit, such as a microcomputer, constituting the control unit. By allowing the setting range to be variably set in this way, it is possible to flexibly respond to the specifications, installation conditions, or load characteristics of the voltage regulator, thereby improving the availability of the voltage regulator.

[0016] In a voltage regulating device according to an aspect of the present disclosure, when the current tap position corresponds to a through tap, the setting range for the reference ratio is predetermined within a range from 0 to 0.5.

[0017] In this embodiment, when the current tap position is a through tap, the settling range for the reference ratio is predetermined to a range from 0 to 0.5, so that the circuit voltage of the OLTC circuit (OLTC circuit voltage) can correspond to 0 V, which is the theoretical value for the circuit voltage of the OLTC circuit when the tap position is a through tap. In other words, when the tap position corresponds to a through tap, the circuit voltage of the OLTC circuit (OLTC circuit voltage) is assumed to correspond to the theoretical value of 0 V, and the voltage ratio in this case may be calculated by dividing the OLTC circuit voltage value by the secondary voltage value (through tap: voltage ratio = OLTC circuit voltage value / secondary voltage value). In this case, by setting the settling range for the reference ratio to a range from 0 to 0.5, the effects of errors or disturbances in voltage measurement can be eliminated, enabling efficient abnormality detection of the change-over switch (thyristor). In addition, the control unit may calculate the voltage ratio by dividing the OLTC circuit voltage value by the secondary voltage value (voltage ratio = OLTC circuit voltage value / secondary voltage value) even when the current tap position is other than a through tap.

[0018] In a voltage regulating device according to an aspect of the present disclosure, the secondary side voltage value is a voltage value on the load side.

[0019] In this aspect, the control unit acquires the voltage of the low-voltage distribution line to which the load is connected, that is, the voltage value on the load side, as the secondary-side voltage value. A measurement transformer is provided on the low-voltage distribution line to which the load is connected, i.e., the secondary distribution line, and the control unit can obtain the voltage value on the load side from the measurement transformer on the secondary distribution line (secondary measurement transformer).

[0020] In a voltage regulating device according to an aspect of the present disclosure, the secondary voltage value is a tap voltage value of the regulating transformer.

[0021] In this aspect, the control unit acquires the tap voltage of the regulating transformer, i.e., the voltage value between two taps (tap voltage value) among the multiple taps provided in the regulating transformer, as the secondary-side voltage value. The control unit may acquire the voltage value between the two taps (tap voltage value) from a measurement transformer (inter-tap measurement transformer) arranged between the taps. For example, the regulating transformer is an autotransformer that shares a portion of its primary winding and secondary winding, and has two taps drawn out from one end and the other end, and a middle tap located between the one end and the other end and dividing the winding into a series winding and a shunt winding. As an example, the number of turns from the tap at one end to the middle tap is set to twice the number of turns from the tap at the other end to the middle tap. When the tap voltage value of the regulating transformer is the voltage value between one end tap and an intermediate tap (tap voltage value), the control unit can calculate the secondary voltage value by tripling the acquired tap voltage value (tap voltage value × 3). The tripled factor is calculated by dividing the number of turns of the winding by the number of turns from one end tap to the intermediate tap. The control unit then uses the voltage ratio between the secondary voltage value calculated by tripling the tap voltage value and the circuit voltage value of the OLTC circuit (OLTC circuit voltage value) to determine whether the changeover switch (thyristor) is faulty, thereby enabling efficient fault detection. The measurement transformer (inter-tap measurement transformer) located between the taps may function as a power supply for the microcontroller constituting the control unit or for the power supply board on which the control unit is mounted. By configuring the inter-tap measurement transformer as part of the power supply in this way, the number of components can be reduced and the product size can be made smaller.

[0022] In a voltage adjustment device according to one aspect of the present disclosure, when the control unit determines that the changeover switch is abnormal, it performs a protective process by temporarily changing the tap position to a through tap.

[0023] In this aspect, if the calculated voltage ratio does not fall within the settling range based on the reference ratio corresponding to the current tap position, the control unit determines that the changeover switch is abnormal. The control unit then temporarily sets the tap position to a through tap, thereby protecting the voltage regulator. That is, if the control unit determines that any of the changeover switches is abnormal, the control unit temporarily sets the tap position to a through tap, and sets the voltage applied to the OLTC circuit to a theoretical value of zero, thereby effectively protecting the voltage regulator. The control unit may temporarily, i.e., after a predetermined period (protection period) has elapsed, continue or resume the process of determining the target tap position and switching the tap to the target tap position, using, for example, an integral method or a definite-time method according to the deviation time from the dead band.

[0024] In one aspect of the voltage adjustment device of the present disclosure, when the control unit determines that any of the multiple changeover switches is abnormal a predetermined number of times, it disables the any of the changeover switches and continues to control the tap switching.

[0025] In this aspect, if the calculated voltage ratio does not fall within the settling range based on the reference ratio corresponding to the current tap position, the control unit determines that the changeover switch is abnormal and identifies the changeover switch selected (ON) for setting that tap position as the abnormal changeover switch. After determining the abnormality, the control unit performs protection processing, for example, temporarily changing the tap position to a through tap, and then resumes tap switching using, for example, an integration method corresponding to the deviation time from the dead band. At this time, if the abnormal changeover switch identified in the previous abnormality determination is determined to be abnormal again and the same changeover switch is determined to be abnormal a predetermined number of times, for example, three times, the control unit disables the changeover switch. In this way, the control unit disables the changeover switch when an event that determines that any of the multiple changeover switches is abnormal occurs consecutively and the number of times that the changeover switch has been determined to be abnormal reaches a predetermined number. The control unit then continues tap switching using only the other changeover switches (changeover switches that have not been continuously determined to be abnormal a predetermined number of times) other than the disabled changeover switch, for example, using an integration method or the like depending on the deviation time from the dead band. In this way, the changeover switch that has been continuously determined to be abnormal a predetermined number of times is disabled, and the abnormal changeover switch is essentially separated from the on-load tap changer, thereby eliminating any impact on the voltage regulator. Furthermore, for example, if the tap position is a through tap, multiple combinations are possible with each changeover switch, so tap switching control can be continued using changeover switches other than the disabled changeover switch. [Effects of the Invention]

[0026] The voltage regulator can efficiently determine whether the changeover switch is abnormal. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a block diagram showing an example of the configuration of a voltage adjusting device according to a first embodiment (secondary-side measurement transformer). [Figure 2]FIG. 2 is a circuit diagram showing an example of the configuration of a changeover switch. [Figure 3] FIG. 10 is an explanatory diagram of a tap position table that defines the relationship between the tap position and the reference ratio. [Figure 4] 10 is a flowchart showing a processing procedure of a control unit. [Figure 5] FIG. 10 is a block diagram showing a configuration example of a voltage adjustment device according to a second embodiment (tap measurement transformer). DETAILED DESCRIPTION OF THE INVENTION

[0028] (Embodiment 1) Hereinafter, embodiments will be described with reference to the drawings. Fig. 1 is a block diagram showing an example of the configuration of a voltage adjustment device according to embodiment 1 (secondary-side measurement transformer). Voltage adjustment device (TVR: Thyristor type Step Voltage Regulator)) 100 adjusts the voltage of single-phase AC supplied from a power source side (primary side) such as a power plant or substation on the left side of the page, and distributes the single-phase AC to a load side (secondary side) on the right side of the page via distribution lines 1u and 1v.

[0029] The voltage regulator 100 includes series transformers 11 and 12, whose secondary windings 112 and 122 are connected in series to the power distribution lines 1u and 1v, respectively, and a regulating transformer 2 (tapped transformer) whose winding 20 is connected in parallel to the power distribution lines 1u and 1v. The secondary winding 112 of the series transformer 11 is provided on the power distribution line 1u, and the secondary winding 122 of the series transformer 12 is provided on the power distribution line 1v; that is, the voltage regulator 100 includes two series transformers 11 and 12. The voltage regulator 100 further includes an on-load tap changer 3 provided between the winding 20 of the regulating transformer 2 and the primary windings 111 and 121 of the series transformers 11 and 12, respectively. The on-load tap changer 3 and the regulating transformer 2 constitute an on-load tap-changing transformer 200.

[0030] In the series transformers 11 and 12, primary windings 111 and 121 correspond to secondary windings 112 and 122, respectively. The primary windings 111 and 121 are connected in parallel so that voltages of opposite phases are induced in the secondary windings 112 and 122, respectively. The terminals of the primary windings 111 and 121 corresponding to the load-side terminals of the secondary windings 112 and 122, respectively, are designated as u1 and v1. Furthermore, the terminals of the primary windings 111 and 121 corresponding to the power-supply-side terminals of the secondary windings 112 and 122, respectively, are designated as u2 and v2.

[0031] The regulating transformer 2 is an autotransformer, with a primary winding and a portion of the secondary winding shared. The regulating transformer 2 has a winding 20 connected between the power distribution lines 1u and 1v. The winding 20 of the regulating transformer 2, which is an autotransformer, includes a series winding 20a (Nt1) and a shunt winding 20b (Nt2), and the series winding 20a (Nt1) and the shunt winding 20b (Nt2) are separated by an intermediate tap t2. Regarding the number of turns of the shunt winding 20b (Nt2) and the series winding 20a (Nt1), the number of turns of the shunt winding 20b (Nt2) may be greater than the number of turns of the series winding 20a (Nt1) (Nt2>Nt1). In this case, the number of turns of the primary winding is the sum (Nt1+Nt2) of the series winding 20a (Nt1) and the shunt winding 20b (Nt2). The number of turns of the secondary winding varies depending on the tap position.

[0032] The winding 20 has taps t1 and t3 drawn out from one end and the other end, and an intermediate tap t2 located between the one end and the other end that divides the winding 20 into a series winding 20a (Nt1) and a shunt winding 20b (Nt2). One of the taps t1 to t3 of the winding 20 is connected to the primary terminals u2 and v1 of the series transformer 1a via the on-load tap changer 3, and the other tap, which may be the same as or different from the tap t1, is connected to the primary terminals u1 and v2 of the series transformer 1a via the on-load tap changer 3. Connecting the same tap to each terminal on the primary side of the series transformer 1a is the case when a through tap is used.

[0033] In this embodiment, the regulating transformer 2 is an autotransformer, but is not limited to this and may be a compound transformer. When the regulating transformer 2 is a compound transformer, the primary winding 21 is connected between the distribution lines 1u and 1v. The secondary winding 22 corresponding to the primary winding 21 has taps t1 and t3 drawn out from one end and the other end, and an intermediate tap t2 drawn out from between the one end and the other end, and tap control is performed in the same way as when the regulating transformer 2 is an autotransformer.

[0034] In order to measure the voltage applied to winding 20 of regulating transformer 2, a primary winding of secondary measurement transformer PT2 may be connected between distribution lines 1u and 1v (secondary distribution line) on the load side (secondary side) of the series transformer. The secondary measurement transformer PT2 can measure the secondary voltage value indicating the voltage on the load side. Furthermore, a primary winding of primary measurement transformer PT1 may be connected between distribution lines 1u and 1v (primary distribution line) on the power supply side (primary side) of the series transformer. The primary measurement transformer PT1 can measure the primary voltage value indicating the voltage on the power supply side. Instead of primary measurement transformer PT1 and secondary measurement transformer PT2, a resistor voltage divider or other means may be used to detect the voltage between distribution lines 1u and 1v.

[0035] The on-load tap changer 3 has six change-over switches ThA, ThB, ThC, Th1, Th2, and Th3 for switching taps t1 to t3 of the winding 20 of the regulating transformer 2. The configuration of the on-load tap changer 3 is not limited to that shown in Fig. 1, and may be configured to include, for example, a polarity-switching tap selection switch that switches the polarity of the voltage applied to the series transformer 1a.

[0036] These multiple switches ThA, ThB, ThC, Th1, Th2, and Th3 constitute an OLTC circuit 4. A circuit measurement transformer PT3 is connected to the OLTC circuit 4, detecting the voltage of the OLTC circuit 4 (the voltage value applied to the OLTC circuit 4). The circuit measurement transformer PT3 is connected to connection lines 3u and 3v included in the OLTC circuit 4 so as to be parallel to the triac Tr1 or the ignition circuit Tg1 (described later). In other words, the circuit measurement transformer PT3 detects the voltage across the triac Tr1 or the ignition circuit Tg1 (the potential difference across the two ends). Thus, the OLTC circuit 4 includes multiple switches ThA, ThB, ThC, Th1, Th2, and Th3, and the circuit measurement transformer PT3. One end of the circuit measurement transformer PT3 is connected to the connection line 3u, and the other end is connected to the connection line 3v.

[0037] The on-load tap changer 3 further has a control unit 31 that controls the switching of each of the above-mentioned changeover switches, and a drive unit 32 that drives each changeover switch to ON based on a drive signal from the control unit 31. The control unit 31 is connected to the primary side measurement transformer PT1, the secondary winding of the secondary side measurement transformer PT2, and the circuit measurement transformer PT3, and may also be connected to the secondary winding of a current transformer CT1 (corresponding to a current detection unit) described below.

[0038] The control unit 31 is configured, for example, by a microcomputer or the like, and has a CPU (Central Processing Unit) (not shown) and a storage unit such as ROM or RAM. The control unit 31 controls voltage adjustment according to a control program pre-stored in the storage unit such as ROM. Information temporarily or ultimately generated by the control unit 31, such as various voltage values ​​acquired from the primary measurement transformer PT1, the secondary winding of the secondary measurement transformer PT2, and the circuit measurement transformer PT3, and intermediate and result data generated in performing various calculations, may be stored in the storage unit such as RAM. The storage unit stores a tap position table (described later) and various integer constants or constants referenced by the control unit 31 when performing various calculations. The control unit 31 has a timer counter for measuring elapsed time.

[0039] Tap t1 of winding 20 is connected to one end of change-over switches ThA and Th1 via a protective fuse (not shown; the same applies below), tap t2 is connected to one end of change-over switches ThB and Th2 via a fuse, and tap t3 is connected to one end of change-over switches ThC and Th3 via a fuse. The other ends of change-over switches ThA, ThB, and ThC are connected to terminals u1 and v2 on the primary side of series transformer 1a via connection line 3u. The other ends of change-over switches Th1, Th2, and Th3 are connected to terminals u2 and v1 on the primary side of series transformer 1a via connection line 3v.

[0040] Between the connection wires 3u and 3v, a series circuit of a current-limiting resistor RS and a fault correction switch ThS is connected to both ends of a triac Tr1 (a semiconductor switch). An ignition circuit Tg1 is connected to both ends of the triac Tr1, and the voltage across the triac Tr1 is supplied to the ignition circuit Tg1. The output of the ignition circuit Tg1 is connected to the gate of the triac Tr1.

[0041] A primary winding of a current transformer CT1 may be coupled to the connecting wire 3u on the output side of the connection point between the triac Tr1 and the series circuit in order to measure the single-phase AC line current output by the on-load tap changer 3. The primary winding of CT1 may be coupled to the connecting wire 3v to measure the single-phase AC line current.

[0042] The fault correction switch ThS connects and disconnects the current-limiting resistor RS between the taps to maintain fault correction between the taps through the current-limiting resistor RS during the process of switching the taps t1 to t3. The triac Tr1 is fired when an overcurrent is detected to protect the changeover switches, or when the operation of the on-load tap changer 3 is stopped. In this case, fault correction is performed between terminals u1 and u2 and between terminals v1 and v2 on the primary side of the series transformer 1a, preventing the primary side of the series transformer 1a from becoming open.

[0043] By providing the current transformer CT1 in the above-described position, it is possible to measure the current flowing through the transfer switch and the fault correction switch ThS. When the triac Tr1 is fired, the current transformer CT1 can measure the current flowing from the primary windings 111 and 121 of the series transformer 1a to the triac Tr1. This makes it possible to calculate the maximum current flowing through the distribution lines 1u and 1v, for example, in the event of a short-circuit fault in the distribution lines 1u and 1v. If it is not necessary to measure the current flowing through the triac Tr1, the location of the current transformer CT1 is not limited to the above-described location, and it may be located closer to the winding 20 than the connection point of the connection line 3u with the triac Tr1. While the present embodiment has been described using the triac Tr1, this is not limiting, and a circuit in which two thyristors are connected in anti-parallel may be used instead of the triac Tr1.

[0044] FIG. 2 is a circuit diagram showing an example of the configuration of the change-over switch ThA. The configuration of each switch will be described using the change-over switch ThA as an example. The same applies to the other change-over switches and the fault correction switch ThS. The change-over switch ThA is formed by connecting thyristors ThAa and ThAb in antiparallel, each conducting in one direction from the anode to the cathode. The anode of thyristor ThAa and the cathode of thyristor ThAb are connected to a connection line 3u. The cathode of thyristor ThAa and the anode of thyristor ThAb are connected to tap t1 of winding 20 of the regulating transformer 2. The gates of thyristors ThAa and ThAb are connected to a driver 32. When a trigger signal is applied from the driver 32 to the gate of each thyristor, the change-over switch ThA becomes bidirectionally conductive. The change-over switch ThA may be formed by a single triac.

[0045] FIG. 3 is an explanatory diagram of a tap position table that defines the relationship between the reference ratio and the tap position. For example, the voltage regulation function of a voltage regulator using this tap position table is ±15V in 5V steps with 7 taps, with the primary rated voltage being 210V and the secondary rated voltage being 210V. In this case, there are seven possible combinations of the changeover switches, which are represented by tap positions from tap 1 to tap 7. For example, when the tap position is set to tap 1, the changeover switches ThC and Th1 are turned on. This connects tap t1 to connecting line 3v, and tap t3 to connecting line 3u. In this case, the number of turns between taps t1 and t3 is equal to the number of turns of the secondary winding 22, and the magnitude of the voltage output by the on-load tap changer 3 is maximized.

[0046] For taps 2 to 3, the changeover switches that connect the two taps to the connection lines 3u and 3v are determined according to the combination of taps such that the number of turns between the taps decreases stepwise. For example, when the tap position is set to tap 3, the changeover switches ThC and Th2 are turned on. This connects tap t2 to the connection line 3v, and tap t3 to the connection line 3u. In this case, the number of turns between taps t2 and t3 is minimum except for 0, and the magnitude of the voltage output by the on-load tap changer 3 is minimum except for 0.

[0047] When the tap position is set to tap 4, the changeover switches ThA and Th1 are turned on. This connects tap t1 to the connection lines 3u and 3v. In this case, the voltage output by the on-load tap changer 3 becomes 0. This is what is called a through tap. Note that the changeover switches for setting the through tap are not limited to the changeover switches ThA and Th1, but may be the changeover switches ThB and Th2, or the changeover switches ThC and Th3.

[0048] For taps 5 to 7, the changeover switches that connect two taps to the connecting wires 3u and 3v are determined according to the combination of taps such that the number of turns between the taps increases stepwise. For example, when the tap position is tap 7, the changeover switches ThA and Th3 are turned on. This connects tap t1 to the connecting wire 3u, and tap t3 to the connecting wire 3v. In this case, the number of turns between taps t1 and t3 is equal to the number of turns of the secondary winding 22, and the magnitude of the voltage output by the on-load tap changer 3 is maximized. However, compared to the case of tap 1, the phase of the output voltage is reversed.

[0049] As described above, the number of turns between the two taps connected to the connection lines 3u and 3v by tap changing is determined according to the tap position, in other words, the turns ratio of the regulating transformer 2 is determined according to the tap position. The turns ratio here refers to the ratio of the number of turns of the primary winding 21 to the number of turns between the two taps connected to the connection lines 3u and 3v by tap changing (turns ratio).

[0050] The tap position table is stored in advance in a memory unit of the control unit 31, which is configured with a microcomputer or the like. That is, the memory unit associates the tap position determined by tap switching with a value related to the turns ratio of the regulating transformer at that tap position, and stores this as a tap position table (table format). Each time the tap position is raised or lowered, the tap position table is referenced and the information indicating the changeover switch to be turned on and the turns ratio are read out, thereby facilitating the tap switching process.

[0051] The tap position table includes management items (fields), such as tap position (tap voltage), selection state, reference ratio, and settling range (normal range). The tap position field stores the tap position number and tap voltage according to the state of the changeover switch. In this embodiment, the tap position takes values ​​from 1 to 7, and the number of tap positions (number of taps) is seven (7 taps).

[0052] The reference ratio field stores the reference ratio corresponding to the tap position (tap position stored in the same record). The selection status field stores the selection status of the tap corresponding to the tap position (tap position stored in the same record). When the tap position (tap voltage) is 1 (225V) or 7 (195V), the 70V tap is selected and the reference ratio is 3.0. When the tap position (tap voltage) is 2 (220V) or 6 (200V), the 140V tap is selected and the reference ratio is 2.0. When the tap position (tap voltage) is 3 (215V) or 5 (205V), the 210V tap is selected and the reference ratio is 3.0. When the tap position (tap voltage) is 4 (210V), the clear tap is selected and the reference ratio is 0, in which case the protection state is entered.

[0053] The setting range (normal range) field stores the setting range corresponding to the reference ratio. When the tap position is 1 to 3 or 5 to 7, i.e., other than a through tap, the setting range is set to, for example, ±10%, and the range defined by ±10% for each reference ratio is set as the normal range. Therefore, when the reference ratio is 3.0, the setting range (normal range) is 2.7 to 3.3. When the reference ratio is 2.0, the setting range (normal range) is 1.8 to 2.2. When the reference ratio is 1.0, the setting range (normal range) is 0.9 to 1.1. When the tap position is 4, i.e., a through tap, the setting range is set to, for example, a setting value (e.g., 0.5) that is added to 0, and the setting range (normal range) is 0 to 0.5.

[0054] The management items (fields) of the tap position table may further include changeover switches Th1, Th2, Th3, ThA, ThB, and ThC to be turned on (closed) (selected) according to the tap position. In this case, the field of the changeover switch stores the combination of AC switch elements (changeover switches Th1, Th2, Th3, ThA, ThB, and ThC) to be selected. In other words, the number of the changeover switch Th1, Th2, Th3, ThA, ThB, or ThC to be turned on at the corresponding tap position may be stored.

[0055] 4 is a flowchart showing the processing procedure of the control unit 31. The control unit 31 executes this processing in a cycle shorter than one cycle of 60 Hz, for example, during operation of the on-load tap changer 3, i.e., during execution of control to change the tap, in accordance with a control program (program product) stored in advance in a storage unit such as a ROM.

[0056] The control unit 31 acquires the circuit voltage value of the OLTC circuit 4 (S101). The OLTC circuit 4 is provided with a circuit measurement transformer PT3 that detects the circuit voltage value (OLTC circuit voltage value) applied to the OLTC circuit 4. In this embodiment, the circuit measurement transformer PT3 is connected to the connection lines 3u and 3v so as to be in parallel with the triac Tr1 or the ignition circuit Tg1, etc. The circuit measurement transformer PT3 outputs the detected OLTC circuit voltage value to the control unit 31. The control unit 31 may store the OLTC circuit voltage value acquired from the circuit measurement transformer PT3 in a memory unit in association with the time of acquisition, i.e., the time of detection by the circuit measurement transformer PT3.

[0057] The control unit 31 acquires the secondary voltage value (S102). A secondary measurement transformer PT2 that detects the secondary voltage value of the secondary distribution line, i.e., the low-voltage distribution line, of the voltage adjustment device 100 is provided. The secondary measurement transformer PT2 outputs the detected secondary voltage value to the control unit 31. The control unit 31 may store the secondary voltage value acquired from the secondary measurement transformer PT2 in a memory unit in association with the time of acquisition, i.e., the time of detection by the secondary measurement transformer PT2.

[0058] The control unit 31 calculates the voltage ratio between the circuit voltage value and the secondary voltage value (S103). The control unit 31 calculates the voltage ratio between the circuit voltage value (OLTC circuit voltage value) detected at substantially the same time and the secondary voltage value. The control unit 31 may store the calculated voltage ratio in the storage unit in association with the detection times of the OLTC circuit voltage value and the secondary voltage value. The control unit 31 may calculate the voltage ratio between the circuit voltage value (OLTC circuit voltage value) and the secondary voltage value by, for example, dividing the secondary voltage value by the circuit voltage value (OLTC circuit voltage value) (secondary voltage value ÷ OLTC circuit voltage value). Furthermore, when the current tap position is a through tap, for example, the control unit 31 may calculate the voltage ratio by dividing the OLTC circuit voltage value by the secondary voltage value (voltage ratio = OLTC circuit voltage value / secondary voltage value). The reference ratio to be compared with the voltage ratio is predetermined depending on the calculation method of the voltage ratio.

[0059] The control unit 31 acquires a reference ratio corresponding to the current tap position (S104). When controlling tap switching by turning on or off the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC, the control unit 31 stores the current tap position in a storage unit. Alternatively, the control unit 31 stores the on / off states (open / closed states) of the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC corresponding to the current tap position in the storage unit. The control unit 31 identifies the current tap position by referring to the storage unit, and derives a reference ratio corresponding to the current tap position by referring to a tap position table based on the identified tap position.

[0060] The control unit 31 determines whether the voltage ratio is within a predetermined settling range for the reference ratio (S105). The tap position table includes the settling range for the reference ratio in addition to the reference ratio corresponding to the current tap position. The settling range for the reference ratio corresponds to the normal range, and the control unit 31 determines whether the calculated voltage ratio falls within the settling range (normal range) for the reference ratio.

[0061] If the voltage ratio is within the setting range (S105: YES), the control unit 31 determines that the change-over switches Th1, Th2, Th3, ThA, ThB, and ThC are normal (S106). If the voltage ratio is within the setting range, i.e., if it falls within the setting range (normal range) for the reference ratio, the control unit 31 determines that at least the change-over switches Th1, Th2, Th3, ThA, ThB, and ThC that are on (closed) when setting the current tap position are normal. In other words, the control unit 31 determines that the change-over switches Th1, Th2, Th3, ThA, ThB, and ThC that were controlled to be on (closed) when setting the current tap position are not in an open state due to a malfunction or the like and are normal.

[0062] If the voltage ratio is not within the settling range (S105: NO), the control unit 31 determines that the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC are abnormal (S1051). If the voltage ratio is not within the settling range, i.e., if the voltage ratio deviates from the settling range (normal range) for the reference ratio, the control unit 31 determines that the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC, which were controlled to be on (closed) when setting the current tap position, are in an open state due to a malfunction or the like and are abnormal. The control unit 31 identifies the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC determined to be abnormal by, for example, referring to the on / off states of the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC or a tap position table stored in the memory unit according to the current tap position, and increments the number of times the changeover switches have been determined to be abnormal (the number of abnormality determinations) by one (increment process) and stores the number of times (the number of abnormality determinations) in the memory unit.

[0063] If the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC previously determined to have an abnormality are different from the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC currently determined to have an abnormality, the control unit 31 may reset (initialize) the number of times that the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC previously determined to have an abnormality to 0. This makes it possible to count the number of times that any of the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC have been consecutively determined to have an abnormality, and therefore it is possible to identify the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC for which an event that causes consecutive abnormality occurs in the same changeover switch Th1, Th2, Th3, ThA, ThB, and ThC and the number of times that the changeover switches have been determined to have an abnormality (number of abnormality determinations) has reached a predetermined number.

[0064] The control unit 31 determines whether the number of determination results for the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC determined to be abnormal has reached a predetermined number (S1052). By continuing the processing in this embodiment, the control unit 31 periodically performs abnormality determination for the multiple changeover switches Th1, Th2, Th3, ThA, ThB, and ThC included in the on-load tap changer 3. As a result, when an event determined to be abnormal occurs consecutively in the same changeover switch Th1, Th2, Th3, ThA, ThB, or ThC among the multiple changeover switches Th1, Th2, Th3, ThA, ThB, and ThC, the control unit 31 determines whether the number of abnormality determination results has reached a predetermined number, for example, three.

[0065] A predetermined number (e.g., three times) indicating a threshold for the number of consecutive abnormality determination results for the same changeover switch Th1, Th2, Th3, ThA, ThB, or ThC is stored in advance in a storage unit or the like, and the control unit 31 can acquire or recognize the predetermined number by referring to the storage unit. As described above, when an abnormality is determined for the same changeover switch Th1, Th2, Th3, ThA, ThB, or ThC, the control unit 31 increments the number of times the switch has been determined to be abnormal (the number of abnormality determinations) by one (increment process) and stores the number of times (the number of abnormality determinations) in the storage unit. The control unit 31 acquires the number of abnormality determinations for the changeover switch Th1, Th2, Th3, ThA, ThB, or ThC determined to be abnormal in the current determination process by referring to the storage unit, and determines whether the number of abnormality determinations has reached the predetermined number.

[0066] When the determination result of the changeover switches Th1, Th2, Th3, ThA, ThB, ThC determined to be abnormal reaches a predetermined number of times (S1052: YES), the control unit 31 disables the changeover switches Th1, Th2, Th3, ThA, ThB, ThC determined to be abnormal (S1053). When the determination result of the changeover switches Th1, Th2, Th3, ThA, ThB, ThC determined to be abnormal reaches a predetermined number of times, that is, when the number of events determined to be abnormal in any of the changeover switches Th1, Th2, Th3, ThA, ThB, ThC reaches a predetermined number of times, the control unit 31 disables the changeover switches Th1, Th2, Th3, ThA, ThB, ThC determined to be abnormal. The control unit 31 disables the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC that are determined to be abnormal, so that, for example, when the tap position is to be a through tap, a changeover switch other than the disabled changeover switches Th1, Th2, Th3, ThA, ThB, and ThC may be used.

[0067] In this embodiment, when the number of consecutive determination results of the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC that are determined to be abnormal reaches a predetermined number, for example, three times, the control unit 31 disables the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC that are determined to be abnormal and continues the tap changing process, but this is not limited to this. The control unit 31 may also stop operation of the on-load tap changer 3 when the number of consecutive determination results of the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC that are determined to be abnormal reaches a predetermined number (for example, three times).

[0068] If the number of times that the switch Th1, Th2, Th3, ThA, ThB, or ThC is determined to be abnormal has not reached the predetermined number (S1052: NO), or after the process of S1053, The control unit 31 executes a protection process by temporarily changing the tap position to a through tap (S1054). If the number of times that the determination result for the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC determined to be abnormal has not reached a predetermined number, or if the process of S1053 has been performed, i.e., if any of the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC is determined to be abnormal (S1051), the control unit 31 executes a protection process by temporarily changing the tap position to a through tap. By changing the tap position to a through tap, the voltage applied to the OLTC circuit 4 can be set to zero as a theoretical value, thereby effectively performing a protection process for the voltage regulator 100. After executing the protection process, i.e., for a predetermined period (protection process period), the control unit 31 sets the tap position to a through tap, and then continues or resumes the process of determining a target tap position and switching the tap to the target tap position using, for example, an integral method or a fixed-time method according to the deviation time from the dead band.

[0069] 5 is a block diagram showing a configuration example of a voltage adjusting device 100 according to embodiment 2 (tap measurement transformer PT21). Similar to embodiment 1, the voltage adjusting device 100 of embodiment 2 includes an OLTC circuit 4 including a plurality of change-over switches Th1, Th2, Th3, ThA, ThB, and ThC and a circuit measurement transformer PT3, and includes an inter-tap measurement transformer PT21 instead of the secondary side measurement transformer PT2 of embodiment 1.

[0070] The inter-tap measurement transformer PT21 is provided between tap t3 connected to one end of winding 20 in regulating transformer 2 and tap t2, which is the middle tap. If voltage adjustment device 100 is configured to operate at ±15V in 5V steps with 7 taps, with a primary rated voltage of 210V and a secondary rated voltage of 210V, the inter-tap measurement transformer PT21 detects the voltage of the 70V tap in regulating transformer 2. In this way, the inter-tap measurement transformer PT21, which is provided between tap t3 connected to one end of winding 20 in regulating transformer 2 and tap t2, which is the middle tap, may function as a power supply for a power supply board on which a microcomputer and the like constituting control unit 31 are mounted.

[0071] In this embodiment, the control unit 31 determines whether or not there is an abnormality in the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC (thyristors) using the voltage ratio between the voltage value of the 70V tap of the regulating transformer 2 detected by the circuit measurement transformer PT3 and the circuit voltage value (OLTC circuit voltage value) of the OLTC circuit 4, instead of the secondary voltage value from the inter-tap measurement transformer PT21. In this case, the secondary voltage corresponds to the voltage of the 210V tap of the regulating transformer 2, so when calculating the voltage ratio with the OLTC circuit voltage value, the difference is whether the voltage of the regulating transformer 2 is the voltage of the 210V tap or the voltage of the 70V tap. Therefore, by multiplying the voltage value of the 70V tap of the regulating transformer 2 detected by the circuit measurement transformer PT3 by three (3 = (70 + 140) / 70), it can be converted to the voltage of the 210V tap, which corresponds to the secondary voltage, and as in embodiment 1, the secondary voltage value and the circuit voltage value (OLTC circuit voltage value) can be used to determine whether there is an abnormality in the change-over switches Th1, Th2, Th3, ThA, ThB, and ThC (thyristors).

[0072] In this embodiment (embodiments 1 and 2), the number of taps of the regulating transformer 2 is three, but this is not limited to this and the number of taps may be, for example, five taps, etc. Similarly, the tap voltage is not particularly limited and can be applied to various regulating transformers 2. Furthermore, although the voltage regulator 100 has been described as a single-phase voltage regulator 100 that regulates the voltage of a single-phase AC, the present invention is not limited to this and can also be applied to a three-phase voltage regulator 100, with each OLTC circuit 4 to which each line voltage is applied.

[0073] The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include all modifications within the meaning and scope of the claims.

[0074] Multiple claims in the claims section may be combined with each other regardless of the form of reference. Multiple dependent claims are defined in the claims section, depending on multiple claims. Multiple dependent claims may not be defined in the claims section, but multiple dependent claims may be defined that depend on multiple dependent claims. [Explanation of symbols]

[0075] 1u, 1v distribution line, 100 voltage regulator, 11, 12 series transformer, 111, 121 primary winding, 112, 122 secondary winding, u1, u2, v1, v2 terminal, 200 on-load tap changer, 2 regulating transformer, 20 winding, 20a series winding, 20b shunt winding, 21 primary winding, 22 secondary winding, t1, t2, t3 tap, 3 on-load tap changer, 31 control unit (microcomputer, power supply board), 32 drive unit, 4 OLTC circuit, Th1, Th2, Th3, ThA, ThB, ThC changeover switch (thyristor), ThAa, ThAb thyristor, 3u, 3v connecting line, ThS fault correction switch, RS Current limiting resistor, PT1 Primary side measurement transformer, PT2 Secondary side measurement transformer, PT21 Inter-tap measurement transformer (power supply), PT3 Circuit measurement transformer, CT1 Current transformer, Tr1 Triac, Tg1 Firing circuit

Claims

1. a series transformer having a secondary winding connected in series to a distribution line that distributes alternating current from a power source to a load; a regulating transformer having a primary winding connected in parallel to the distribution line; a load tap changer that is provided with a changeover switch for switching and selecting a tap of a winding of the regulating transformer, and that connects the selected tap of the winding to output AC, The on-load tap changer includes a control unit that controls the tap change by turning on or off the changeover switch, The control unit Acquire a circuit voltage value of an OLTC circuit including the change-over switch; Acquire a secondary voltage value on the secondary side; An abnormality determination is made for the changeover switch based on the acquired circuit voltage value and the acquired secondary side voltage value. Voltage regulator.

2. The control unit Calculating a voltage ratio between the circuit voltage value and the secondary voltage value; Based on the result of comparing the calculated voltage ratio with a reference ratio corresponding to the current tap position, an abnormality determination is made for the changeover switch. The voltage regulator of claim 1 .

3. The control unit If the voltage ratio is within a predetermined settling range with respect to the reference ratio, the changeover switch is determined to be normal; If the voltage ratio is outside a predetermined settling range with respect to the reference ratio, the changeover switch is determined to be abnormal. The voltage regulator according to claim 2 .

4. The settling range is predetermined as a range of ±10% of the reference ratio. The voltage regulator according to claim 3 .

5. The secondary voltage value is the voltage value on the load side. The voltage regulator according to any one of claims 1 to 4.

6. The secondary voltage value is a tap voltage value of the regulating transformer. The voltage regulator according to any one of claims 1 to 4.

7. The control unit When the changeover switch is determined to be abnormal, it temporarily switches the tap position to a through tap to perform a protective process, When a predetermined number of times have passed since the determination result that any one of the plurality of changeover switches is abnormal, the changeover switch is disabled and control of switching the tap is continued. The voltage regulator according to any one of claims 1 to 4.

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