voltage regulator

Abstract

To provide a voltage adjusting device that does not need to connect a series circuit including a serial switch and a resistor to a terminal of primary winding.SOLUTION: A voltage adjusting device 1 adjusts an effective value of an AC voltage. A switcher 5 switches a tap to be electrically connected to a specific terminal of primary winding 31 among three taps T1, T2, and T3 which are connected to single winding 40. An effective value of an AC voltage between the taps T1 and T2 is adjusted according to an effective value of an AC voltage between two distribution lines U and V. Two pieces of secondary winding 32 included in two series transformers 3u and 3v are arranged in the middle of the two distribution lines U and V. In the switcher 5, a control unit 53 limits a flow direction of a circuit current flowing through an upper side switch circuit in a flow state into a first direction or a second direction according to a current value of the circuit current flowing through the upper side switch circuit in the flow state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a voltage regulator that adjusts the effective value of AC voltage between two distribution lines. This voltage regulator has a tap winding to which multiple taps are connected. One terminal of multiple first switches is connected to each of the multiple taps of the tap winding. One terminal of multiple second switches is also connected to each of the multiple taps of the tap winding. The other terminals of the multiple first switches are connected to one terminal of two primary windings of two transformers. The other terminals of the multiple second switches are connected to the other terminals of two primary windings of the two transformers.

[0003] The two secondary windings of the two transformers are respectively arranged midway between the two distribution lines. With respect to the tap windings, the effective values ​​of the AC voltages output from the two taps are adjusted according to the effective value of the AC voltage between the two distribution lines. When one of the multiple first switches and one of the multiple second switches are switched on, an AC voltage is applied from the tap winding to the two primary windings, and the effective value of the AC voltage between the two distribution lines increases or decreases. When the switched on among the multiple first switches or the multiple second switches is changed, the AC voltage applied to the two primary windings changes, thereby changing the AC voltage output to the outside.

[0004] In the voltage regulator of Patent Document 1, a series circuit of a fault correction switch and a resistor is connected across both ends of the primary winding. When changing which of the multiple first switches or multiple second switches is turned on, the fault correction switch is turned on. Next, which of the multiple first switches or multiple second switches is turned on. Finally, the fault correction switch is turned off. As a result, the flow of current through the primary winding is not interrupted. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-175274 Summary of the Invention [Problem to be solved by the invention]

[0006] In the voltage regulator described in Patent Document 1, when the fault correction switch is on, current flows through the resistor and is consumed. If it were possible to realize a configuration that does not require connecting a series circuit including the fault correction switch and resistor to the terminals of the primary winding, it would be possible to realize a voltage regulator with low power consumption.

[0007] The present invention has been made in view of the above circumstances, and its object is to provide a voltage regulator that does not require a series circuit including a short-circuit switch and a resistor to be connected to the terminals of the primary winding. [Means for solving the problem]

[0008] A voltage adjustment device according to one aspect of the present invention is a voltage adjustment device that adjusts the effective value of an AC voltage, and includes: a tap winding to which multiple taps are connected; multiple transformers having primary and secondary windings; and a switch that switches between taps among the multiple taps to which a specific terminal of the primary winding is electrically connected; the effective value of the AC voltage between two of the multiple taps is adjusted according to the effective value of the AC voltage between two of multiple distribution lines; each of multiple secondary windings of the multiple transformers is disposed midway along the multiple distribution lines; the switch includes multiple switch circuits that switch between a conducting state in which current can flow and a blocking state in which current flow is blocked; and a controller that controls the multiple switch circuits; and the controller limits the direction of flow of a circuit current flowing through the switch circuits in the conducting state to a first direction or a second direction according to the current value of the circuit current flowing through the switch circuits in the conducting state. [Effects of the Invention]

[0009] According to the above embodiment, there is no need to connect a series circuit including a short-circuit switch and a resistor to the terminals of the primary winding. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a circuit diagram of a voltage regulator according to a first embodiment. [Figure 2] FIG. 2 is a circuit diagram of an upper switch circuit and a lower switch circuit. [Figure 3] FIG. 2 is a block diagram showing the configuration of a main part of a controller. [Figure 4] 10 is a timing chart for explaining a change in the conduction state of an upper switch circuit or a lower switch circuit and a restriction on the flow direction of a circuit current. [Figure 5] 10 is a flowchart showing a procedure for a direction restriction process. [Figure 6] 10 is a flowchart showing a procedure for tap switching processing. [Figure 7] FIG. 10 is a circuit diagram of a voltage regulator according to a second embodiment. [Figure 8] FIG. 10 is a circuit diagram of a voltage regulator according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below with reference to the drawings showing embodiments thereof. (Embodiment 1) FIG. 1 is a circuit diagram of a voltage regulator 1 according to a first embodiment. An AC power source 2 is connected between two distribution lines U and V. The AC power source 2 is, for example, a substation, and outputs an AC voltage to the voltage regulator 1 via the two distribution lines U and V. The voltage regulator 1 outputs an AC voltage via the two distribution lines U and V and a neutral line Q. The voltage regulator 1 adjusts the effective value of the AC voltage between the distribution lines U and V on the output side based on the effective value of the AC voltage between the distribution lines U and V on the input side.

[0012] The voltage regulator 1 has two series transformers 3u and 3v, a regulating transformer 4, and a switch 5. In each of the series transformers 3u and 3v, a primary winding 31 and a secondary winding 32 are wound around a magnetic annular core 30. In the regulating transformer 4, an auto-winding 40 is wound around a core (not shown). Three taps T1, T2, and T3 are connected to the auto-winding 40. Taps T1 and T3 are connected to two terminals of the auto-winding 40, respectively. Tap T2 is connected midway through the auto-winding 40. The number of turns of the auto-winding 40 between taps T1 and T2 is different from the number of turns of the auto-winding 40 between taps T2 and T3. The auto-winding 40 functions as a tap winding.

[0013] One terminal of each of the two secondary windings 32 is connected to the input distribution lines U and V. The other terminal of each of the two secondary windings 32 is connected to the output distribution lines U and V. One terminal and the other terminal of one primary winding 31 are connected to one terminal and the other terminal of the other primary winding 31. An auto-winding 40 is connected between the output distribution lines U and V. Taps T1 and T3 are located on the distribution line U and V sides, respectively. One terminal of a neutral conductor Q is connected midway through the auto-winding 40. The number of turns of the auto-winding 40 between the distribution line U and the neutral conductor Q is the same as the number of turns between the distribution line V and the neutral conductor Q.

[0014] The switch 5 includes an assembly 50, a current sensor 51, a voltage sensor 52, and a controller 53. The assembly 50 includes three upper switch circuits A1, A2, and A3 and three lower switch circuits B1, B2, and B3. Hereinafter, any integer is represented by i. The integer i may be 1, 2, or 3. One terminal of each of the upper switch circuit Ai and the lower switch circuit Bi is connected to a tap Ti. The other terminals of each of the three upper switch circuits A1, A2, and A3 are connected to a first connection node between one terminal of the primary winding 31 via a common current sensor 51. The other terminals of each of the three lower switch circuits B1, B2, and B3 are connected to a second connection node between the other terminals of the primary winding 31. In FIG. 1, the first and second connection nodes are located on the right and left sides, respectively. The current sensor 51 is further connected to the controller 53. The voltage sensor 52 is connected to the taps T1 and T2 and the controller 53.

[0015] The controller 53 switches the state of each of the three upper switch circuits A1, A2, A3 and the lower switch circuits B1, B2, B3 between a conducting state in which current can flow and a blocking state in which current flow is blocked. Normally, one of the three upper switch circuits A1, A2, A3 is in a conducting state, and the remaining upper switch circuits are in a blocking state. Similarly, normally, one of the three lower switch circuits B1, B2, B3 is in a conducting state, and the remaining lower switch circuits are in a blocking state. One of three taps T1, T2, T3 is electrically connected to each of the first node and the second node.

[0016] The AC voltage between the output distribution lines U and V is applied to both ends of the single winding 40. The single winding 40 applies a common AC voltage from two of the three taps T1, T2, and T3 to the two primary windings 31. When the conducting state of the upper or lower switch circuit is changed, the effective value or phase of the AC voltage applied by the single winding 40 to the two primary windings 31 is changed.

[0017] When an AC voltage is applied to the two primary windings 31, the two secondary windings 32 increase or decrease the effective value of the AC voltage between the input distribution lines U and V. The AC voltage with the increased or decreased effective value is output to the outside as the AC voltage between the output distribution lines U and V. The method for increasing or decreasing the effective value is well known, so a detailed description of this method will be omitted.

[0018] In FIG. 1, the dashed arrow indicates the direction of current flow when the effective value of the AC voltage increases when the polarity of the voltage of distribution line U is positive relative to the potential of distribution line V. In the primary winding 31, current flows from the first node to the second node. In a similar case, when the effective value of the AC voltage decreases, current flows from the second node to the first node in the primary winding 31. When the polarity of the voltage of distribution line U is negative, the direction of the current is opposite to the direction of the current when the polarity of distribution line U is positive. The greater the effective value of the AC voltage applied to the primary winding 31, the greater the increase or decrease. A change in the direction of current flowing through the primary winding 31 corresponds to a change in the phase of the AC voltage applied to the primary winding 31.

[0019] The controller 53 switches the tap among the three taps T1, T2, and T3 electrically connected to the first node or the second node by changing the conducting state of the upper switch circuit or the lower switch circuit. One terminal and the other terminal of the two primary windings 31 each function as a specific terminal.

[0020] The effective value of the AC voltage between two of the three taps T1, T2, and T3 is adjusted according to the effective value of the AC voltage between the two distribution lines U and V. The effective value of the AC voltage between two taps is expressed as the product of the effective value of the AC voltage between the two distribution lines U and V and the turns ratio. The turns ratio is a value obtained by dividing the number of turns of the single winding 40 between the two taps by the number of turns of the entire single winding 40.

[0021] Voltage sensor 52 detects the voltage value (instantaneous value) of the AC voltage between taps T1 and T2 and outputs a voltage signal indicating the detected voltage value to controller 53. The effective value of the AC voltage between taps T1 and T2 is expressed as the product of the effective value of the AC voltage between output distribution lines U and V and the turns ratio for taps T1 and T2. The phase of the AC voltage between taps T1 and T2 matches the phase of the AC voltage between output distribution lines U and V.

[0022] Hereinafter, the current flowing through the conducting switch circuits among the upper switch circuits A1, A2, and A3 and the lower switch circuits B1, B2, and B3 will be referred to as the circuit current. The current sensor 51 detects the current value (instantaneous value) of the circuit current flowing through the conducting upper switch circuit among the three upper switch circuits A1, A2, and A3. The current sensor 51 outputs a current signal indicating the detected current value to the controller 53. Hereinafter, the flow direction of the circuit current flowing from the assembly 50 to the first node will be referred to as the leftward direction. The flow direction of the circuit current flowing from the first node to the assembly 50 will be referred to as the rightward direction. When the flow direction of the circuit current flowing through the conducting upper switch circuit is the leftward direction, the current value indicated by the current signal is a positive value. When the flow direction of the circuit current flowing through the conducting upper switch circuit is the rightward direction, the current value indicated by the current signal is a negative value.

[0023] 2 is a circuit diagram of an upper switch circuit A1 and a lower switch circuit B2. The configurations of the upper switch circuits A2 and A3 are similar to that of the upper switch circuit A1. The configurations of the lower switch circuits B1 and B3 are similar to that of the lower switch circuit B1. FIG. 2 shows first and second examples of the upper switch circuit A1 and the lower switch circuit B2.

[0024] Each of the upper switch circuits A1, A2, A3 and the lower switch circuits B1, B2, B3 includes a first switch G1, a second switch G2, a first diode D1, and a second diode D2. Each of the first switch G1 and the second switch G2 is an IGBT (Insulated Gate Bipolar Transistor). The first switch G1 is connected in series with the second switch G2. The collector and emitter of the first switch G1 are connected to the cathode and anode of the first diode D1, respectively. Similarly, the collector and emitter of the second switch G2 are connected to the cathode and anode of the second diode D2, respectively. The gates of the first switch G1 and the second switch G2 are each connected to a controller 53.

[0025] In the first example, the anodes of the first diode D1 and the second diode D2 are connected to each other. The collector of the first switch G1 in each of the upper switch circuits A1, A2, and A3 is connected to a first node. The collector of the second switch G2 in each of the upper switch circuits A1, A2, and A3 is connected to a tap T1, T2, or T3. The collector of the first switch G1 in each of the lower switch circuits B1, B2, and B3 is connected to a second node. The collector of the second switch G2 in each of the lower switch circuits B1, B2, and B3 is connected to a tap T1, T2, or T3.

[0026] In the second example, the cathodes of the first diode D1 and the second diode D2 are connected to each other. The emitter of the second switch G2 of each of the upper switch circuits A1, A2, and A3 is connected to the first node. The emitter of the first switch G1 of each of the upper switch circuits A1, A2, and A3 is connected to the taps T1, T2, and T3. The emitter of the second switch G2 of each of the lower switch circuits B1, B2, and B3 is connected to the second node. The emitter of the first switch G1 of each of the lower switch circuits B1, B2, and B3 is connected to the taps T1, T2, and T3.

[0027] The controller 53 switches the first switch G1 on or off by adjusting the voltage on the gate of the first switch G1. Similarly, the controller 53 switches the second switch G2 on or off by adjusting the voltage on the gate of the second switch G2. When the first switch G1 and the second switch G2 are in the on state, current can flow through the collector and emitter in that order. When the first switch G1 and the second switch G2 are in the off state, current is blocked from flowing through the collector and emitter.

[0028] When the controller 53 switches off the first switch G1 and the second switch G2 in the upper switch circuit or the lower switch circuit in the conducting state, the state transitions to the blocking state. When the controller 53 switches on at least one of the first switch G1 and the second switch G2 in the upper switch circuit or the lower switch circuit in the conducting state, the state transitions from the blocking state to the conducting state.

[0029] The controller 53 limits the flow direction of the circuit current to the left by switching the first switch G1 and the second switch G2 off and on, respectively, in the upper switch circuit or the lower switch circuit in a conducting state. When the flow direction is limited to the left, the circuit current flows through the second switch G2 and the first diode D1 in that order. The controller 53 limits the flow direction to the right by switching the first switch G1 and the second switch G2 on and off, respectively, in the upper switch circuit or the lower switch circuit in a conducting state. When the flow direction is limited to the right, the circuit current flows through the first switch G1 and the second diode D2 in that order. The controller 53 removes the restriction on the flow direction by switching on both the first switch G1 and the second switch G2 in the upper switch circuit or the lower switch circuit in a conducting state. The left and right directions correspond to the first and second directions, respectively.

[0030] As shown in Figure 2, when the controller 53 restricts the flow direction of the circuit current flowing through the conductive upper switch circuit to the left, it restricts the flow direction of the circuit current flowing through the conductive lower switch circuit to the right. As a result, the current flows as shown by the solid arrow. Similarly, when the controller 53 restricts the flow direction of the circuit current flowing through the conductive upper switch circuit to the right, it restricts the flow direction of the circuit current flowing through the conductive lower switch circuit to the left. As a result, the current flows as shown by the dashed arrow.

[0031] Therefore, the current value of the leftward circuit current flowing through the conducting upper switch circuit is equal to the current value of the rightward circuit current flowing through the conducting lower switch circuit. Similarly, the current value of the rightward circuit current flowing through the conducting upper switch circuit is equal to the current value of the leftward circuit current flowing through the conducting lower switch circuit.

[0032] The first switch G1 and the second switch G2 may be FETs (Field Effect Transistors). In this case, the drain and source correspond to the collector and emitter, respectively. When the FET is on, current can flow bidirectionally through the drain and source. When the first switch G1 and the second switch G2 are FETs, the parasitic diodes of the first switch G1 and the second switch G2 may be used as the first diode D1 and the second diode D2, respectively. When the first switch G1 and the second switch G2 are on, no current flows through the first diode D1 or the second diode D2.

[0033] 3 is a block diagram showing the main configuration of the controller 53. The controller 53 has a differentiation circuit 60, a zero slope detection circuit 61, a zero current detection circuit 62, and a control circuit 63. The voltage sensor 52 outputs a voltage signal to the differentiation circuit 60. The differentiation circuit 60 outputs a differentiation signal indicating the differentiation value of the AC voltage indicated by the voltage signal, i.e., the AC voltage between taps T1 and T2, to the zero slope detection circuit 61. The zero slope detection circuit 61 outputs a zero slope signal indicating the zero slope point when the differentiation value indicated by the differentiation signal becomes zero to the control circuit 63. When the differentiation value is zero, the gradient of the AC voltage between the distribution lines U and V is 0 degrees.

[0034] The current sensor 51 outputs a current signal to a zero current detection circuit 62 and a control circuit 63. The zero current detection circuit 62 outputs a zero current signal to the control circuit 63, which indicates the current zero point when the current value of the circuit current indicated by the current signal becomes 0 A. The control circuit 63 receives a switching signal that instructs switching of the tap to which one terminal or the other terminal of the primary winding 31 is connected.

[0035] The control circuit 63 controls the gate voltages of the six first switches G1 and the six second switches G2 individually to turn on or off the six first switches G1 and the six second switches G2. The control circuit 63 changes the conducting state of the upper switch circuit or the lower switch circuit and limits the flow direction of the circuit current based on the zero slope signal, the zero current signal, the current signal, or the switching signal.

[0036] The control circuit 63 is preferably configured using a logic circuit or an FPGA (Field Programmable Gate Array), etc. The control circuit 63 has a processing element. The processing element of the control circuit 63 executes a computer program to perform various processes.

[0037] 4 is a timing chart for explaining the change of the conduction state of the upper switch circuit or the lower switch circuit and the restriction of the flow direction of the circuit current. In FIG. 4, the transition of the voltage value indicated by the voltage signal is indicated by a dashed line. The transition of the current value of the circuit current indicated by the current signal is indicated by a thin solid line. The transition of the differential value indicated by the differential signal is indicated by a thick solid line. The voltage value indicated by the voltage signal is the voltage value of tap T1 relative to the potential of tap T2.

[0038] The transition of the voltage value indicated by the voltage signal is the waveform of the AC voltage between taps T1 and T2. The phase of the AC voltage between two of the three taps T1, T2, and T3 matches the phase of the AC voltage between the output distribution lines U and V. When the slope of the AC voltage between taps T1 and T2 is 0 degrees, the differential value indicated by the differential signal is 0. Figure 4 shows the transition of the voltage value indicated by the zero-slope signal. The zero-slope signal indicates a high-level voltage value or a low-level voltage value. In Figure 4, the high-level voltage value and the low-level voltage value are indicated by "H" and "L," respectively. Every time the differential value indicated by the differential signal becomes 0, the voltage value indicated by the zero-slope signal switches to a high-level voltage value or a low-level voltage value.

[0039] The zero current signal also indicates a high-level voltage value or a low-level voltage value. Every time the current value of the circuit current indicated by the current signal becomes 0 A, the voltage value indicated by the zero current signal switches to a high-level voltage value or a low-level voltage value.

[0040] 4 shows the transition of the states of the first switch G1 and the second switch G2 of each of the upper switch circuits A1 and A2, and the transition of the states of the first switch G1 and the second switch G2 of each of the lower switch circuits B2 and B3. In the explanation of FIG. 4, the states of the upper switch circuit A3 and the lower switch circuit B1 are maintained in the cut-off state.

[0041] On the left side of FIG. 4, for the upper switch circuit A1 and the lower switch circuit B2, at least one of the first switch G1 and the second switch G2 is on. Therefore, the upper switch circuit A1 and the lower switch circuit B2 are in a conducting state. One terminal and the other terminal of the primary winding 31 are electrically connected to the taps T1 and T2, respectively. For the upper switch circuit A2 and the lower switch circuit B3, both the first switch G1 and the second switch G2 are off. Therefore, the upper switch circuit A2 and the lower switch circuit B3 are in a cutoff state.

[0042] The first switch G1 of the upper switch circuit A1 in a conducting state is off. Therefore, in the upper switch circuit A1, the flow direction of the circuit current is limited to the left. The second switch G2 of the lower switch circuit B2 in a conducting state is off. Therefore, in the lower switch circuit B2, the flow direction of the circuit current is limited to the right. The current value indicated by the current signal is a positive value.

[0043] When the current value of the circuit current flowing through the conductive upper switch circuit A1 drops to a value less than the positive upper threshold, the control circuit 63 switches the first switch G1 of the upper switch circuit A1 from off to on. Furthermore, the control circuit 63 switches the second switch G2 of the lower switch circuit B2 from off to on. As a result, in the conductive upper switch circuit A1 and the conductive lower switch circuit B2, the first switch G1 and the second switch G2 are on, respectively, and there is no restriction on the flow direction of the circuit current. The circuit current can flow in both directions through the conductive upper switch circuit A1 and the conductive lower switch circuit B2.

[0044] When there is no restriction on the flow direction of the circuit current, when the current value of the circuit current flowing through the conducting upper switch circuit A1 drops to a value equal to or lower than the negative lower threshold, the control circuit 63 switches the second switch G2 of the upper switch circuit A1 from on to off. Furthermore, the control circuit 63 switches the first switch G1 of the lower switch circuit B2 from on to off. As a result, the flow directions of the circuit currents flowing through the upper switch circuit A1 and the lower switch circuit B2 are restricted to the rightward and leftward directions, respectively.

[0045] When the flow direction of the circuit current flowing through the upper switch circuit A1 and the lower switch circuit B2 is limited to the rightward and leftward directions, respectively, and the current value of the circuit current flowing through the upper switch circuit A1 in a conducting state rises to a value exceeding the negative lower threshold, the control circuit 63 switches the second switch G2 of the upper switch circuit A1 from off to on. Furthermore, the control circuit 63 switches the first switch G1 of the lower switch circuit B2 from off to on. This removes the restriction on the flow direction of the circuit current.

[0046] When there is no restriction on the flow direction of the circuit current, if the current value of the circuit current flowing through the conducting upper switch circuit A1 rises to a value equal to or greater than the positive upper threshold, the control circuit 63 switches the first switch G1 of the upper switch circuit A1 from on to off. Furthermore, the control circuit 63 switches the second switch G2 of the lower switch circuit B2 from on to off. As a result, the flow directions of the circuit currents flowing through the upper switch circuit A1 and the lower switch circuit B2 are restricted to the leftward and rightward directions, respectively.

[0047] As described above, the control circuit 63 restricts the flow direction of the circuit current flowing through each of the upper switch circuit A1 and the lower switch circuit B2 in the conducting state to either the left or right direction depending on the current value of the circuit current flowing through the upper switch circuit A1 in the conducting state. When the absolute value of the current value of the circuit current flowing through the upper switch circuit A1 and the lower switch circuit B2 in the conducting state is small, the control circuit 63 removes the restriction on the flow direction of the circuit current. As a result, the flow direction of the circuit current is smoothly changed.

[0048] With respect to the circuit current flowing through the upper switch circuit Ai, the upper threshold corresponds to the first threshold, and the absolute value of the lower threshold corresponds to the second threshold. With respect to the circuit current flowing through the lower switch circuit Bi, the absolute value of the lower threshold corresponds to the first threshold, and the upper threshold corresponds to the second threshold.

[0049] When a switching signal for switching the connection destinations of the one terminal and the other terminal of the primary winding 31 to the taps T2 and T3 is input to the control circuit 63, the control circuit 63 waits until the differentiated value of the differentiated signal becomes 0. When the differentiated value of the differentiated signal becomes 0, the control circuit 63 switches the first switch G1 or the second switch G2 from off to on in the upper switch circuit A2 and the lower switch circuit B3, respectively. As a result, the states of the upper switch circuit A2 and the lower switch circuit B3 transition from a cutoff state to a conducting state.

[0050] 4, when the slope is zero, the second switch G2 of the upper switch circuit A1 and the first switch G1 of the lower switch circuit B2 are on. Therefore, the control circuit 63 switches on the second switch G2 of the upper switch circuit A2 and the first switch G1 of the lower switch circuit B3. As a result, the flow direction of the circuit current flowing through the upper switch circuits A1 and A2 is limited to the left. The flow direction of the circuit current flowing through the lower switch circuits B2 and B3 is limited to the right.

[0051] At this time, because the upper switch circuits A1 and A2 and the lower switch circuits B2 and B3 are in a conducting state, the flow of current through the primary winding 31 is not interrupted. Furthermore, the flow direction of the circuit current flowing through the upper switch circuits A1 and A2 is restricted to the same direction. The flow direction of the circuit current flowing through the lower switch circuits B2 and B3 is also restricted to the same direction. Therefore, no short circuit occurs between any two of the three taps T1, T2, and T3. Therefore, there is no need to connect a series circuit in which a short-circuit switch and resistor are connected in series between both terminals of the primary winding 31. Because no current flows through the short-circuit resistor, power consumption is low.

[0052] When the first switch G1 of the upper switch circuit A1 and the second switch G2 of the lower switch circuit B2 are on at the time when the slope is zero, the control circuit 63 switches on the first switch G1 of the upper switch circuit A2 and the second switch G2 of the lower switch circuit B3.

[0053] After the upper switch circuits A1, A2 and the lower switch circuits B2, B3 transition to the conductive state, the control circuit 63 switches off the first switch G1 and the second switch G2 that are on for each of the upper switch circuit A1 and the lower switch circuit B2. As a result, the upper switch circuit in the conductive state among the upper switch circuits A1, A2, A3 is changed to the upper switch circuit A2. The lower switch circuit in the conductive state among the lower switch circuits B1, B2, B3 is changed to the lower switch circuit B3.

[0054] Thereafter, the control circuit 63 restricts the flow direction of the circuit current flowing through each of the upper switch circuit A2 and the lower switch circuit B3 in the conducting state to the left or right, depending on the current value of the circuit current flowing through the upper switch circuit A2 in the conducting state. The method for restricting the flow direction of the circuit current flowing through each of the upper switch circuits A2 and A3 in the conducting state is the same as the method for restricting the flow direction of the circuit current flowing through the upper switch circuit A1 in the conducting state. The method for restricting the flow direction of the circuit current flowing through each of the lower switch circuits B1 and B3 in the conducting state is the same as the method for restricting the flow direction of the circuit current flowing through the lower switch circuit B2 in the conducting state.

[0055] The control circuit 63 of the controller 53 executes a computer program to perform a direction restriction process and a tap changing process. The direction restriction process is a process for restricting the direction of flow of the circuit current flowing through each of the upper switch circuits and the lower switch circuits in a conducting state. The conducting upper switch circuit is appropriately changed among the three upper switch circuits A1, A2, and A3. Similarly, the conducting lower switch circuit is appropriately changed among the three lower switch circuits B1, B2, and B3. The tap changing process is a process for changing the tap to which at least one of one terminal and the other terminal of the primary winding 31 is electrically connected.

[0056] 5 is a flowchart showing the procedure of the direction restriction process. In the direction restriction process, the control circuit 63 first determines whether the current value of the circuit current indicated by the current signal is less than an upper threshold value (step S1). Next, if the control circuit 63 determines that the current value of the circuit current is less than the upper threshold value (S1: YES), it determines whether the current value of the circuit current indicated by the current signal is equal to or greater than a lower threshold value (step S2). As described above, the lower threshold value is a negative value.

[0057] When the control circuit 63 determines that the current value of the circuit current is equal to or greater than the upper threshold (S1: NO), or when the control circuit 63 determines that the current value of the circuit current is less than the lower threshold (S2: NO), the control circuit 63 determines whether the flow direction of the circuit current flowing through the upper switch circuit and the lower switch circuit in the conducting state is restricted (step S3).When the control circuit 63 determines that the flow direction is not restricted (S3: NO), the control circuit 63 restricts the flow direction of the circuit current flowing through the upper switch circuit and the lower switch circuit in the conducting state (step S4).

[0058] In step S4, the control circuit 63 switches off one of the first switch G1 and the second switch G2 for each of the upper and lower switch circuits in the conducting state. When the first switch G1 is switched off, the conducting direction is limited to the leftward direction. When the second switch G2 is switched off, the conducting direction is limited to the rightward direction. When the circuit current indicated by the current signal rises to a value equal to or greater than the upper threshold, in step S4, the conducting direction of the circuit current flowing through each of the upper and lower switch circuits in the conducting state is limited to the leftward and rightward directions. When the circuit current indicated by the current signal falls to a value less than the lower threshold, in step S4, the conducting direction of the circuit current flowing through each of the upper and lower switch circuits in the conducting state is limited to the rightward and leftward directions.

[0059] When the control circuit 63 determines that the current value of the circuit current is equal to or greater than the lower threshold (S2: YES), it determines whether the flow direction of the circuit current flowing through the conducting upper switch circuit and the conducting lower switch circuit is restricted (step S5). When the control circuit 63 determines that the flow direction is restricted (S5: YES), it removes the restriction on the flow direction of the circuit current flowing through the conducting upper switch circuit and the conducting lower switch circuit (step S6). Specifically, in step S6, for each of the conducting upper switch circuit and the conducting lower switch circuit, the first switch G1 and the second switch G2 that are off are turned on.

[0060] When the control circuit 63 determines that the current direction is restricted (S3: YES), it executes one of steps S4 and S6, or when it determines that the current direction is not restricted (S5: NO), it ends the direction restriction process. After completing the direction restriction process, the control circuit 63 executes the direction restriction process again. By executing the direction restriction process by the control circuit 63, the direction of flow of the circuit current flowing through the upper switch circuit and the lower switch circuit in the conducting state is restricted, as shown in FIG.

[0061] 6 is a flowchart showing the steps of the tap switching process. In the tap switching process, the control circuit 63 determines whether or not a switching signal has been input (step S11). If the control circuit 63 determines that a switching signal has not been input (S11: NO), it executes step S11 again. The control circuit 63 waits until a switching signal is input.

[0062] When the control circuit 63 determines that a switching signal has been input (S11: YES), it determines whether the differential value indicated by the differential signal is 0 (step S12). When the control circuit 63 determines that the differential value is not 0 (S12: NO), it executes step S12 again. The control circuit 63 waits until the differential value of the differential signal becomes 0.

[0063] When the control circuit 63 determines that the differential value is 0 (S12: YES), it determines whether the flow direction of the circuit current flowing through the upper switch circuit and the lower switch circuit in the conducting state is restricted (step S13).When the control circuit 63 determines that the flow direction of the circuit current is restricted (S13: YES), it determines whether the difference between the two zero points is less than a certain difference threshold (step S14).

[0064] One zero point is a zero slope point. The other zero point is a zero current point. In step S14, the difference between the two zero points is, for example, the difference between the previous zero slope point detected before the current zero slope point detected in step S12 and the first zero current point detected after the previous zero slope point. In step S14, the control circuit 63 determines whether the restriction on the current direction will be lifted in the near future.

[0065] The control circuit 63 may regard the difference between the two most recent peak points of the sinusoidal waveforms indicated by the differential signal and the current signal as the difference between two zero points.

[0066] When the control circuit 63 determines that the flow direction is not restricted (S13: NO), or when it determines that the difference between the two zero points is less than the difference threshold value (S14: YES), it determines whether the flow direction of the circuit current flowing through each of the upper and lower switch circuits in the conducting state is restricted (step S15). When the control circuit 63 determines that the flow direction is not restricted (S15: NO), it executes step S15 again. In the direction restriction process, the control circuit 63 waits until the flow direction is restricted.

[0067] When the control circuit 63 determines that the difference between the two zero points is equal to or greater than the difference threshold (S14: NO), or when it determines that the current flow direction is restricted (S15: YES), it changes at least one of the upper switch circuit and the lower switch circuit in a conducting state (step S16). As described in the description of FIG. 4, the control circuit 63 changes the state of the upper switch circuit in a blocked state to a conducting state, and then changes the state of the upper switch circuit in a conducting state to a blocked state. This changes the conducting state of the upper switch circuit. The control circuit 63 changes the conducting state of the lower switch circuit in the same way as the conducting state of the upper switch circuit.

[0068] After executing step S16, the control circuit 63 ends the tap changing process. After finishing the tap changing process, the control circuit 63 executes the tap changing process again.

[0069] In each of the series transformers 3u and 3v, when the gradient of the AC voltage applied from the single winding 40 to both ends of the primary winding 31 is 0 degrees, the residual magnetic flux remaining in the core 30 is 0 [Wb]. When the gradient of the output of the single winding 40 becomes 0 degrees, the control circuit 63 changes the conductive state of at least one of the upper and lower switch circuits. Therefore, after the conductive state of at least one of the upper and lower switch circuits is changed, the magnetic flux in the core 30 of each of the series transformers 3u and 3v changes from 0 [Wb]. Therefore, in each of the series transformers 3u and 3v, the magnetic flux in the core 30 is unlikely to exceed the saturation magnetic flux.

[0070] While the magnetic flux of the core 30 exceeds the saturation magnetic flux, the impedance of the two primary windings 31 is significantly low. As a result, an excessive current flows through each of the two primary windings 31. In the voltage regulator 1, the magnetic flux of each of the two cores 30 is unlikely to exceed the saturation magnetic flux, so the possibility of an excessive current flowing through the primary winding 31 is low.

[0071] If the conducting upper switch circuit or the conducting lower switch circuit is changed when the direction of the circuit current flowing through each of the conducting upper switch circuit and the conducting lower switch circuit is not restricted, there is a possibility that two of the three taps T1, T2, and T3 will be short-circuited. If the difference between the two zero points is small, the voltage regulator 1 waits without changing the conducting upper switch circuit or the conducting lower switch circuit until the direction of the current is restricted. Therefore, it is unlikely that the conducting upper switch circuit or the conducting lower switch circuit will be changed when the direction of the circuit current is not restricted.

[0072] (Embodiment 2) In the first embodiment, the number of distribution lines is two. However, the number of distribution lines is not limited to two and may be three. The following describes the differences between embodiment 2 and embodiment 1. Except for the configuration described below, the other configurations are common to embodiment 1, and therefore the same reference numerals as in embodiment 1 are used for the components common to embodiment 1, and the description thereof will be omitted.

[0073] FIG. 7 is a circuit diagram of a voltage regulator 1 according to a second embodiment. In the second embodiment, in addition to distribution lines U and V, a distribution line W is connected to an AC power source 2. The AC power source 2 outputs three AC voltages to the voltage regulator 1 via three distribution lines U, V, and W. The voltage regulator 1 includes a series transformer 3w in addition to two series transformers 3u and 3v. The series transformer 3w has a configuration similar to that of the series transformer 3u. The AC power source 2 and one terminal of a secondary winding 32 of the series transformer 3w are connected by the input distribution line W. The other terminal of the secondary winding 32 of the series transformer 3w is connected to the output distribution line W. The secondary windings 32 of the three series transformers 3u, 3v, and 3w adjust the effective values ​​of the three AC voltages related to the output distribution lines U, V, and W. When the effective values ​​of the three AC voltages of the input distribution lines U, V, and W change, the effective values ​​of the three AC voltages of the output distribution lines U, V, and W also change.

[0074] The voltage regulator 1 further includes two regulating transformers 4a and 4b. Each of the regulating transformers 4a and 4b includes a primary winding 41 and a secondary winding 42. The primary winding 41 and the secondary winding 42 are wound around, for example, an annular core. The primary winding 41 of the regulating transformer 4a is connected between the distribution lines U and V. The primary winding 41 of the regulating transformer 4b is connected between the distribution lines V and W. The two primary windings 41 are connected in a V-connection. Three taps T1, T2, and T3 are connected to the secondary windings 42 of each of the regulating transformers 4a and 4b. Each secondary winding 42 functions as a tap winding.

[0075] Each of the regulating transformers 4a and 4b outputs an AC voltage from two taps connected to the secondary winding 42. The effective value of this AC voltage is expressed as the product of the effective value of the AC voltage applied across the primary winding 41 and the turns ratio. Here, the turns ratio is expressed as (the number of turns between the two taps) / (the number of turns of the primary winding 41). The AC voltage between the output distribution lines U and V is applied across the primary winding 41 of the regulating transformer 4a. The AC voltage between the output distribution lines V and W is applied across the primary winding 41 of the regulating transformer 4b. The phase of the AC voltage between the taps T1 and T2 of the regulating transformer 4a matches the phase of the AC voltage between the output distribution lines U and V. The phase of the AC voltage between the taps T1 and T2 of the regulating transformer 4b matches the phase of the AC voltage between the output distribution lines V and W.

[0076] The switch 5 has two assemblies 50a and 50b configured similarly to the assembly 50 of embodiment 1. The assembly 50a, like the assembly 50 of embodiment 1, is connected to three taps T1, T2, and T3 connected to the secondary winding 42 of the regulating transformer 4a. The assembly 50b, like the assembly 50 of embodiment 1, is connected to three taps T1, T2, and T3 connected to the secondary winding 42 of the regulating transformer 4b.

[0077] One terminal of each of the three primary windings 31 functions as a specific terminal. The specific terminal of the primary winding 31 of the series transformer 3u is connected to the upper switch circuits A1, A2, and A3 of the assembly 50a. The specific terminal of the primary winding 31 of the series transformer 3v is connected to the lower switch circuits B1, B2, and B3 of the assembly 50a and the upper switch circuits A1, A2, and A3 of the assembly 50b. The specific terminal of the primary winding 31 of the series transformer 3w is connected to the lower switch circuits B1, B2, and B3 of the assembly 50b. The other terminal of one primary winding 31 is connected to the other terminals of the remaining two primary windings. The three primary windings 31 are connected in a Y-connection.

[0078] The switch 5 has two current sensors 51a and 51b and two voltage sensors 52a and 52b. The current sensors 51a and 51b detect the current value of the circuit current flowing through the conducting upper switch circuits of the assemblies 50a and 50b, respectively. The voltage sensors 52a and 52b detect the voltage value (instantaneous value) of the AC voltage between the taps T1 and T2 of the regulating transformers 4a and 4b, respectively.

[0079] The switch 5 has a controller 53, similar to the first embodiment. The controller 53 changes the states of the six upper switch circuits A1, A2, A3 and the six lower switch circuits B1, B2, B3 of the assemblies 50a and 50b, respectively. In this way, the controller 53 switches the taps, among the six taps T1, T2, T3 connected to the two secondary windings 42, to which three specific terminals of the three primary windings 31 are electrically connected.

[0080] The controller 53 controls the states of the upper switch circuits A1, A2, A3 and the lower switch circuits B1, B2, B3 of the assembly 50a based on the detection values ​​detected by the current sensor 51a and the voltage sensor 52a, in the same manner as in the first embodiment. The controller 53 controls the states of the upper switch circuits A1, A2, A3 and the lower switch circuits B1, B2, B3 of the assembly 50b based on the detection values ​​detected by the current sensor 51b and the voltage sensor 52b, in the same manner as in the first embodiment. The assemblies 50a and 50b correspond to the assembly 50. The current sensors 51a and 51b correspond to the current sensor 51. The voltage sensors 52a and 52b correspond to the voltage sensor 52. The voltage regulator 1 in the second embodiment achieves the same effects as the voltage regulator 1 in the first embodiment.

[0081] (Embodiment 3) In the second embodiment, the number of regulating transformers is 2. However, the number of regulating transformers may be 3. The following describes the differences between embodiment 3 and embodiment 2. Except for the configuration described below, the other configurations are common to embodiment 2, and therefore the same reference numerals as in embodiment 2 are used for the components common to embodiment 2, and the description thereof will be omitted.

[0082] FIG. 8 is a circuit diagram of a voltage regulator 1 according to the third embodiment. Compared to the second embodiment, the voltage regulator 1 further includes a regulating transformer 4c configured similarly to the regulating transformer 4a. A primary winding 41 of the regulating transformer 4c is connected between the distribution lines U and W. The three primary windings 41 are delta-connected. An AC voltage between the output distribution lines U and W is applied to both ends of the primary winding 41 of the regulating transformer 4c. Three taps T1, T2, and T3 are connected to a secondary winding 42 of the regulating transformer 4c. The secondary windings 42 of the three regulating transformers 4a, 4b, and 4c each function as a tap winding.

[0083] Compared to the second embodiment, the switch 5 further includes an assembly 50c configured similarly to the assembly 50 of the first embodiment. One terminal of each of the three primary windings 31 functions as a specific terminal. The other terminal of the primary winding 31 of the series transformer 3u is connected to a specific terminal of the primary winding 31 of the series transformer 3w. The other terminal of the primary winding 31 of the series transformer 3v is connected to a specific terminal of the primary winding 31 of the series transformer 3u. The other terminal of the primary winding 31 of the series transformer 3w is connected to a specific terminal of the primary winding 31 of the series transformer 3v. The three primary windings 31 are delta-connected. Like the assembly 50a of the second embodiment, the assembly 50c is connected to three taps T1, T2, and T3 that are connected to the secondary winding 42 of the regulating transformer 4c.

[0084] Specific terminals of the primary winding 31 of the series transformer 3w are connected to the upper switch circuits A1, A2, and A3 of the assembly 50a. Specific terminals of the primary winding 31 of the series transformer 3v are connected to the upper switch circuits A1, A2, and A3 of the assembly 50b. Specific terminals of the primary winding 31 of the series transformer 3u are connected to the upper switch circuits A1, A2, and A3 of the assembly 50c.

[0085] The switch 5 further includes a current sensor 51c and a voltage sensor 52c. The current sensor 51c detects the value of the circuit current flowing through the conducting upper switch circuit of the assembly 50c. The voltage sensor 52c detects the voltage value (instantaneous value) of the AC voltage between taps T1 and T2 of the regulating transformer 4c.

[0086] The controller 53 of the switch 5 changes the states of the nine upper switch circuits A1, A2, A3 and the nine lower switch circuits B1, B2, B3 of the assemblies 50a, 50b, 50c, respectively, thereby switching the taps to which three specific terminals of the three primary windings 31 are electrically connected, among the nine taps T1, T2, T3 connected to the three secondary windings 42.

[0087] The controller 53 controls the states of the upper switch circuits A1, A2, A3 and the lower switch circuits B1, B2, B3 of the assembly 50c based on the detection values ​​detected by the current sensor 51c and the voltage sensor 52c, in the same manner as in the first embodiment. The assembly 50c corresponds to the assembly 50. The current sensor 51c corresponds to the current sensor 51. The voltage sensor 52c corresponds to the voltage sensor 52. The voltage adjusting device 1 in the third embodiment achieves the same effects as the voltage adjusting device 1 in the second embodiment.

[0088] In the first to third embodiments, the number of taps provided in the tap winding is not limited to three and may be two or four or more. For each of the assemblies 50, 50a, 50b, and 50c, the number of upper switch circuits is the same as the number of taps connected to one tap winding. The number of lower switch circuits is also the same as the number of taps connected to one tap winding. The voltage value of the AC voltage detected by each of the voltage sensors 52, 52a, 52b, and 52c is not limited to the voltage value of the AC voltage between taps T1 and T2. There is no problem as long as the voltage value of the AC voltage detected by each of the voltage sensors 52, 52a, 52b, and 52c is the voltage value of the AC voltage between two taps connected to one winding.

[0089] The technical features (constituent elements) described in the first to third embodiments can be combined with each other, and by combining them, new technical features can be formed. The disclosed embodiments 1 to 3 are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the meaning described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0090] 1 voltage regulator, 3u, 3v, 3w series transformer, 5 switch, 31 primary winding, 32 secondary winding, 40 single winding (tap winding), 42 secondary winding (tap winding), 53 controller, A1, A2, A3 upper switch circuit, B1, B2, B3 lower switch circuit, D1 First diode, D2 Second diode, G1 First switch, G2 Second switch

Claims

1. A voltage regulator that adjusts the effective value of an AC voltage, a tap winding to which a plurality of taps are connected; a plurality of transformers having primary and secondary windings; a selector for selecting a tap among the plurality of taps to which a specific terminal of the primary winding is electrically connected; Equipped with an effective value of an AC voltage between two of the plurality of taps is adjusted according to an effective value of an AC voltage between two of the plurality of distribution lines; a plurality of secondary windings of the plurality of transformers are respectively arranged midway through the plurality of distribution lines; The switch is a plurality of switch circuits whose states are switched between a conducting state in which current can flow and a blocking state in which current flow is blocked; a controller that controls the plurality of switch circuits; and The controller limits the flow direction of the circuit current flowing through the switch circuit in the conducting state to a first direction or a second direction according to a current value of the circuit current flowing through the switch circuit in the conducting state. Voltage regulator.

2. Each switch circuit is A first switch; a second switch connected in series with the first switch; a first diode connected across the first switch; a second diode connected across the second switch; and the cathodes or anodes of the first diode and the second diode are connected to each other; The controller In the switch circuit in the conducting state, the first switch and the second switch are switched off and on, respectively, to limit the conducting direction to the first direction; In the switch circuit in the conducting state, the first switch and the second switch are switched on and off, respectively, to limit the conducting direction to the second direction. The voltage regulator of claim 1 .

3. The controller When the absolute value of the current value of the circuit current falls to a value less than a first threshold value in a case where the flow direction of the circuit current is limited to the first direction, the restriction on the flow direction of the circuit current is removed, When the absolute value of the current value of the circuit current falls to a value less than a second threshold value in a case where the flow direction of the circuit current is limited to the second direction, the restriction on the flow direction of the circuit current is removed, When there is no restriction on the flow direction and the absolute value of the current value of the circuit current whose flow direction is the first direction increases to a value equal to or greater than the first threshold value, the flow direction of the circuit current is restricted to the first direction; When there is no restriction on the flow direction and the absolute value of the current value of the circuit current whose flow direction is the second direction increases to a value equal to or greater than the second threshold value, the flow direction of the circuit current is restricted to the second direction. The voltage regulator according to claim 1 or 2.

4. The controller changes the switch circuit in the conducting state among the plurality of switch circuits when the gradient of the AC voltage between the two taps connected to the tap winding becomes 0 degrees. The voltage regulator according to any one of claims 1 to 3.

5. The controller When the gradient becomes 0 degrees, it is determined whether or not a difference between a point in time when the gradient becomes 0 degrees and a point in time when a current value of the circuit current flowing through the switch circuit in the conducting state becomes 0 A is less than a difference threshold value; When it is determined that the difference is less than the difference threshold, the current flow direction of the switch circuit in the current-conducting state is restricted, and then the switch circuit in the current-conducting state is changed among the plurality of switch circuits.

5. The voltage regulator according to claim 4.

Images