Rectifier device

Abstract

To provide a rectifier device capable of reducing the possibility of shortening the life of a tap switch.SOLUTION: A rectifier device includes: a first transformer equipped with a tap changer for switching taps; a second transformer that receives the output of the first transformer; a wiring bus bar through which the output current of the second transformer flows; a diode rectifier connected to the wiring bus bar; a saturable reactor disposed between the second transformer and the diode rectifier, through which the wiring bus bar passes; a power supply that supplies control current to a control winding wound around the saturable reactor; a detector that detects the voltage generated in the control winding; and a control unit that switches the taps in accordance with a detected value of the voltage.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a rectifying device. [Background technology]

[0002] A system is known that includes a tapped transformer connected to an AC system, a diode rectifier that rectifies the output of the tapped transformer, an arithmetic and control device that determines the voltage step to be changed based on the output current of the diode rectifier and a predetermined DC current set value, and a tap changer control device that controls the switching of the tap of the tapped transformer based on the determined voltage step (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-177985 Summary of the Invention [Problem to be solved by the invention]

[0004] As the number of tap changes in a tapped transformer increases, the life of the tap changer decreases.

[0005] The present disclosure provides a rectifier that prevents shortened tap changer life. [Means for solving the problem]

[0006] The rectifier device of the first aspect is a first transformer with a tap changer for changing taps; a second transformer to which the output of the first transformer is input; a wiring bus bar through which the output current of the second transformer passes; a diode rectifier connected to the wiring bus bar; a saturable reactor disposed between the second transformer and the diode rectifier, through which the wiring bus bar passes; a power supply that supplies a control current to a control winding wound around the saturable reactor; a detector for detecting a voltage generated in the control winding; and a control device that switches the tap in accordance with the detected value of the voltage. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to prevent the life of the tap changer from being shortened. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing an example of the configuration of a rectifier according to a first comparative example. [Figure 2] FIG. 2 is a detailed diagram of the output current control device. [Figure 3] 10 is a diagram illustrating an example of the relationship between the control current flowing through the control winding and the output voltage of the diode rectifier. FIG. [Figure 4] 10 is a diagram for explaining the movement of a characteristic curve showing the relationship between a control current flowing through a control winding and an output voltage of a diode rectifier. FIG. [Figure 5] 1 is a diagram illustrating an example of a configuration of a rectifier according to a first embodiment. [Figure 6] 10 is a diagram illustrating an example of the relationship between the control current flowing through the control winding and the output voltage of the diode rectifier. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Configuration of Rectifier According to First Comparative Example> 1 is a diagram showing an example of the configuration of a rectifier device according to a first comparative example. Rectifier device 200 includes a voltage regulating transformer 101 connected to a three-phase system, a rectifier transformer 102 connected downstream of voltage regulating transformer 101, a VCR system 104 connected downstream of rectifier transformer 102, and a diode rectifier 103 connected to the output of VCR system 104. VCR is an abbreviation for voltage regulating reactor.

[0010] Voltage regulating transformer 101 is an example of a first transformer equipped with a tap changer that switches taps. Voltage regulating transformer 101 has tap changer 101b that switches tap 101a in response to switching signal 122 (described below). Rectifier transformer 102 is an example of a second transformer to which the output of the first transformer is input. VCR system 104 includes saturable reactor 106 through which wiring bus bar 107, through which the output current of rectifier transformer 102 passes, passes. Saturable reactor 106 is disposed between the output portion of rectifier transformer 102 and the AC input portion of diode rectifier 103.

[0011] The diode rectifier 103 has an AC input section connected to a wiring bus bar 107 through which the output current of the rectifier transformer 102 passes. The diode rectifier 103 rectifies the AC current input to the AC input section and supplies DC power to a load such as an electrolytic cell. A DC current transformer (DCCT) 105 is installed at the DC output section of the diode rectifier 103. The DCCT 105 supplies a measurement signal of the DC current output from the diode rectifier 103 to an output current control device 111.

[0012] The output current controller 111 controls the DC current supplied to the load so that it is equal to the current setting value 112. The output current controller 111 includes a VCR control circuit 113, a bias control circuit 115, a tap changing controller 121, and an automatic current controller (ACR) 131.

[0013] VCR control circuit 113 is a component of VCR system 104. VCR control circuit 113 passes smoothed control current 114 through saturable reactor 106 to constrain and magnetize saturable reactor 106, thereby controlling the voltage borne by saturable reactor 106. VCR control circuit 113 sends measurement signal 123 of control current 114 to tap switching control device 121.

[0014] The bias control circuit 115 is a component of the VCR system 104. The bias control circuit 115 applies a smoothed bias current 116 to the saturable reactor 106 to magnetize the saturable reactor 106.

[0015] The VCR control circuit 113 and the bias control circuit 115 magnetize the saturable reactor 106 in opposite directions. The voltage borne by the saturable reactor 106 depends on the difference between the control current 114 and the bias current 116.

[0016] The tap switching control device 121 detects that the voltage borne by the saturable reactor 106 has become excessively large (or excessively small), and sends a switching signal 122 for the tap 101 a provided in the voltage adjustment transformer 101 to the voltage adjustment transformer 101 .

[0017] The automatic current control device 131 sends a control signal 132 to the VCR control circuit 113 so that the measured value of the direct current obtained by the DCCT 105 (measured value of the DCCT 105 ) becomes equal to the current setting value 112 .

[0018] <Operation of the output current control device 111> The output current controller 111 controls the DC current supplied to the load so that it is equal to the current setting value 112. For this purpose, the ACR 131 and the VCR control circuit 113 automatically control the control current 114 to control the voltage borne by the saturable reactor 106 and to control the output voltage of the diode rectifier 103 (phase angle control). When the voltage borne by the saturable reactor 106 approaches saturation or becomes very small, the tap changing controller 121 changes the tap 101a of the voltage regulating transformer 101. The output current controller 111 operates at the new tap voltage of the voltage regulating transformer 101.

[0019] <Detailed configuration of output current control device 111> Fig. 2 is a detailed diagram of the output current control device 111. However, Fig. 2 shows only one arm of the saturable reactor 106 and the diode rectifier 103.

[0020] The saturable reactor 106 has a core through which the wiring bus bar 107 passes, and a control winding 148 and a bias winding 149 are provided on the core.

[0021] The VCR control circuit 113 includes a DC reactor 141, a shunt 142, a thyristor rectifier 143, and a tapped single-phase transformer 144. The DC reactor 141 smoothes the control current 114 and performs pinned magnetization on the saturable reactor 106. The shunt 142 measures the control current 114. The thyristor rectifier 143 rectifies the AC output from the tapped single-phase transformer 144 and controls the control current 114 in accordance with a control signal 132 from the ACR 131. The tapped single-phase transformer 144 has multiple taps. One of these taps is set at the on-site location to a position appropriate for the resistance of the VCR control circuit 113 (such as the resistance of the cable and the resistance of the DC reactor 141).

[0022] The bias control circuit 115 includes a DC reactor 145, a diode rectifier 146, and a svariac 147. The DC reactor 145 smoothes the bias current 116 and restricts magnetization of the saturable reactor 106. The diode rectifier 146 rectifies the AC current output from the svariac 147. The bias current 116 is adjusted by operating the svariac 147.

[0023] <Operation of the Rectifier According to the First Comparative Example> Fig. 3 is a diagram illustrating the relationship between the control current 114 flowing through the control winding 148 and the output voltage of the diode rectifier 103. The mechanism for controlling the output voltage of the diode rectifier 103 will be described below with reference to Fig. 3. Fig. 3 illustrates the case where the bias current 116 is zero.

[0024] The voltage borne by the saturable reactor 106 increases as the control current 114 increases, resulting in a decrease in the output voltage of the diode rectifier 103.

[0025] When the measurement value of DCCT 105 is greater than current setting value 112, ACR 131 sends a control signal 132 to thyristor rectifier 143 to increase control current 114. When the measurement value of DCCT 105 is less than current setting value 112, ACR 131 sends a control signal 132 to thyristor rectifier 143 to decrease control current 114.

[0026] The thyristor rectifier 143 performs phase angle control in accordance with the control signal 132 of the ACR 131 , and controls the control current 114 .

[0027] The tap changing controller 121 operates in accordance with the measurement signal 123 of the control current 114 as shown in the following steps S1 to S5.

[0028] S1: The operating points for switching the tap of voltage adjustment transformer 101 are points A and B. The output voltage change range of diode rectifier 103 (voltage range controlled by VCR control circuit 113) is 100%. Point A, where the tap up command is output, is set to a position 10 to 20% lower than the upper limit of the output voltage change range. Point B, where the tap down command is output, is set to a position 10 to 20% higher than the lower limit of the output voltage change range.

[0029] S2: The shunt 142 measures the control current 114 at the operating point and sends a measurement signal 123 of the control current 114 to the tap changing controller 121.

[0030] S3: The tap changing controller 121 uses the measurement signal 123 to determine whether the state in which the control current 114 deviates from the control current range between points A and B continues for a predetermined time. If the state in which the control current 114 is lower than the lower limit current at point A continues for a predetermined time, the tap changing controller 121 sends a tap-up switching signal 122 to the voltage adjustment transformer 101. If the state in which the control current 114 is higher than the upper limit current at point B continues for a predetermined time, the tap changing controller 121 sends a tap-down switching signal 122 to the voltage adjustment transformer 101.

[0031] S4: The voltage regulating transformer 101 switches the tap in accordance with the tap switching signal 122. As the tap of the voltage regulating transformer 101 increases, the output voltage of the voltage regulating transformer 101 increases. As the tap of the voltage regulating transformer 101 decreases, the output voltage of the voltage regulating transformer 101 decreases.

[0032] S5: The diode rectifier 103 operates steadily between points A and B.

[0033] The bias current 116 is set by adjusting the slidac 147 before operation of the rectifier 200. The bias current 116 does not change during operation of the rectifier 200. As the bias control circuit 115 changes the magnitude of the bias current 116, the characteristic curve shown in FIG. 3 moves along the horizontal axis of the control current 114.

[0034] Bias control circuit 115 sets bias current 116 to the rated current of VCR control circuit 113. This generates a characteristic curve that indicates the relationship "when control current 114 is increased, the output voltage of diode rectifier 103 increases." Furthermore, if a deviation occurs in the "relationship between control current 114 flowing through control winding 148 and the output voltage of diode rectifier 103" in Figure 3, bias control circuit 115 makes an adjustment to reduce the deviation.

[0035] 3 may move along the horizontal axis of control current 114 depending on the magnitude of the output current of diode rectifier 103. This state is shown in FIG.

[0036] FIG. 4 is a diagram for explaining the movement of a characteristic curve showing the relationship between the control current 114 flowing through the control winding 148 and the output voltage of the diode rectifier 103. In FIG.

[0037] Characteristic A1 is the characteristic curve during factory testing. The positions of the tap-up command and tap-down command are determined relative to characteristic A1. The operating range is voltage control width A2. Due to differences in production processes and production factories, factory testing is sometimes performed using the product diode rectifier 103 and sometimes using a test rectifier.

[0038] Characteristic B1 is the characteristic curve during actual operation (operation in which products are produced at a customer factory). The output current during actual operation is several tens of times that during factory testing. The reverse recovery characteristics of the diodes used in diode rectifier 103 change when the flow current is large. Due to this reverse recovery characteristic, characteristic A1 shifts to the left along the horizontal axis of control current 114 and changes to characteristic B1. If the positions of the tap-up command and tap-down command are the same as during factory testing, the operating range is voltage control width B2.

[0039] Characteristic C1, like characteristic B1, is a characteristic curve during actual operation, but it is a characteristic curve for products with different (varying) diode and saturable reactor characteristics. If the positions of the tap-up command and tap-down command are the same as in factory testing, the operating range is voltage control width C2. Whether the product's characteristics are characteristic B1 or characteristic C1 cannot be determined at the factory testing stage.

[0040] As shown in Figure 4, the voltage control widths of the characteristics B1 and C1 are smaller than those of the characteristic A1. In particular, the voltage control width of the characteristic C1 is small, and the output voltage of the diode rectifier 103 can be controlled only about half as much as that of the characteristic A1. As a result, the tap switching signal 122 is sent frequently, and the number of tap changes of the voltage adjustment transformer 101 increases.

[0041] To prevent this problem, it is conceivable to adjust the bias current 116 at the start of normal operation to bring the characteristic B1 or characteristic C1 closer to the characteristic A1. However, this adjustment would be performed during normal operation. Adjusting the bias current 116 during normal operation could have an adverse effect on production. Alternatively, in a plant where multiple rectifiers are connected in parallel, there is a risk that the control could become unstable during this adjustment, causing all of the rectifiers to trip. For this reason, adjusting the bias current 116 during normal operation is often not permitted.

[0042] Therefore, the rectifier 200 according to the first comparative example operates with the bias current 116 set to a preset value. As a result, the number of tap changes in the voltage adjustment transformer 101 increases beyond the normal value, which may shorten the life of the tap changer 101b. To solve this problem, it is necessary to create a tap changing method that automatically follows any changes in the "relationship between the control current 114 and the output voltage of the diode rectifier 103" and does not require any adjustment.

[0043] <Configuration of the rectifier according to the first embodiment> Fig. 5 is a diagram showing an example of the configuration of a rectifier according to the first embodiment. A rectifier 200 according to the first comparative example adjusts the timing for switching the tap of a voltage adjustment transformer 101 up or down in accordance with the magnitude of a control current 114. In contrast, a rectifier 201 shown in Fig. 5 adjusts the timing for switching the tap of a voltage adjustment transformer 101 up or down in accordance with the magnitude of the voltage of a saturable reactor 106.

[0044] The first embodiment will be described below. In the first embodiment, the description of the same configuration, action, and effect as the first comparative embodiment will be omitted or simplified by citing the above description.

[0045] Fig. 5 shows only one arm of the saturable reactor 106 and the diode rectifier 103. The rectifier 201 shown in Fig. 5 does not include the bias winding 149 and the bias control circuit 115 in the rectifier 200 according to the first comparative example. However, the rectifier 201 may include the bias winding 149 and the bias control circuit 115, if necessary.

[0046] The voltage detector 152 is connected to both ends of the control winding 148 and detects the voltage generated in the control winding 148 (the AC voltage generated in the saturable reactor 106). The voltage detector 152 sends a measurement signal 153 indicating the detected value of the voltage generated in the control winding 148 (the AC voltage generated in the saturable reactor 106) to the tap switching control device 121.

[0047] The voltage detector 152 detects the voltage generated in the control winding 148 (the AC voltage generated in the saturable reactor 106) by detecting the voltage between the first detection point 48a before the control winding 148 is wound around the saturable reactor 106 and the second detection point 48b after the control winding 148 is wound around the saturable reactor 106.

[0048] Although not shown in Fig. 5, the control winding 148 between the first detection point 48a and the second detection point 48b is also wound around the cores of the other arms of the saturable reactor 106, as shown in Fig. 1. Therefore, the voltage detector 152 rectifies a plurality of set voltages and reset voltages generated by each core of the saturable reactor 106 to detect the voltage generated in the control winding 148 (the AC voltage generated in the saturable reactor 106).

[0049] The voltage detector 152, for example, rectifies and smoothes the AC voltage (set voltage and reset voltage) of the saturable reactor 106, and divides the smoothed voltage to obtain a detection value of the voltage generated in the control winding 148 (the AC voltage generated in the saturable reactor 106).

[0050] The voltage detector 152 includes, for example, a diode rectifier 52a that rectifies the AC voltage (set voltage and reset voltage) of the saturable reactor 106, a filter circuit 52b that smoothes the output voltage of the diode rectifier 52a, and a voltage divider circuit 52c that resistively divides the output voltage of the filter circuit 52b. The voltage detector 152 may also include a surge absorption circuit 52d that absorbs surge voltages superimposed on the output voltage of the diode rectifier 52a.

[0051] The tap changing control device 121 switches the tap 101a in response to a measurement signal 153 indicating a detected value of the voltage generated in the control winding 148 (the AC voltage generated in the saturable reactor 106). The tap changing control device 121 switches the tap 101a in response to the magnitude of the detected value.

[0052] The rectifier 201 includes a programmable power supply 151 and a DC reactor 141 as a VCR control circuit that controls the saturable reactor 106. The programmable power supply 151 is a continuously variable power supply that can continuously supply the control current 114 from a negative rated current to a positive rated current. The programmable power supply 151 serves both as a control power supply that supplies the control current 114 and as a bias power supply that supplies a bias current. The programmable power supply 151 can be easily configured using, for example, a PWM inverter. The programmable power supply 151 may be a commercially available product.

[0053] The programmable power supply 151 is a DC power supply capable of supplying positive and negative control current 114, but the DC power supply that supplies the control current 114 may be a DC power supply that cannot supply negative control current 114. For example, the DC power supply (thyristor rectifier 143 and tapped single-phase transformer 144) in FIG. 2 may be used instead of the programmable power supply 151. However, when a DC power supply that cannot supply negative control current 114 is used, the control current 114 is controlled so as not to reach the negative region even if the "relationship between the control current 114 and the output voltage of the diode rectifier 103" in FIG. 4 changes.

[0054] <Operation of the rectifier according to the first embodiment> 6 is a diagram illustrating the relationship between the control current 114 flowing through the control winding 148 and the output voltage of the diode rectifier 103. The mechanism for controlling the output voltage of the diode rectifier 103 will be described below with reference to FIG.

[0055] The voltage borne by the saturable reactor 106 increases as the control current 114 increases, resulting in a decrease in the output voltage of the diode rectifier 103.

[0056] When the measured value of the DCCT 105 is larger than the current setting value 112, the ACR 131 sends a control signal 132 to the programmable power supply 151 to increase the control current 114. When the measured value of the DCCT 105 is smaller than the current setting value 112, the ACR 131 sends a control signal 132 to the programmable power supply 151 to decrease the control current 114.

[0057] The programmable power supply 151 controls the control current 114 according to the control signal 132 of the ACR 131 .

[0058] The tap changing controller 121 operates in accordance with the measurement signal 153 of the voltage detector 152 as shown in the following steps S11 to S15.

[0059] S11: The operating points for switching the tap of the voltage adjustment transformer 101 are points A and B. The output voltage change range of the diode rectifier 103 (the voltage change range controlled by the VCR control circuit 113) is 100%. Point A, where the tap increase command is output, is set to a position 10 to 20% lower than the upper limit of the output voltage change range. Point B, where the tap decrease command is output, is set to a position 10 to 20% higher than the lower limit of the output voltage change range.

[0060] S12: The voltage detector 152 measures the burden voltage of the saturable reactor 106 at the operating point and sends a measurement signal 153 to the tap changing control device 121. The voltage detector 152 can easily measure the burden voltage of the saturable reactor 106 by rectifying the AC voltage (set voltage and reset voltage) generated across the control winding 148.

[0061] S13: The tap changing control device 121 uses the measurement signal 153 to determine whether the state in which the burden voltage of the saturable reactor 106 deviates from the voltage range between points A and B continues for a predetermined time. If the state in which the burden voltage of the saturable reactor 106 is higher than the upper limit voltage corresponding to the output voltage of the diode rectifier 103 at point A continues for a predetermined time, the tap changing control device 121 sends a tap-up switching signal 122 to the voltage adjustment transformer 101. If the state in which the burden voltage of the saturable reactor 106 is lower than the lower limit voltage corresponding to the output voltage of the diode rectifier 103 at point B continues for a predetermined time, the tap changing control device 121 sends a tap-down switching signal 122 to the voltage adjustment transformer 101.

[0062] S14: The voltage regulating transformer 101 switches the tap in accordance with the tap switching signal 122. As the tap of the voltage regulating transformer 101 increases, the output voltage of the voltage regulating transformer 101 increases. As the tap of the voltage regulating transformer 101 decreases, the output voltage of the voltage regulating transformer 101 decreases.

[0063] S15: The diode rectifier 103 operates steadily between points A and B.

[0064] <Effects of the rectifier according to the first embodiment> As described above, the rectifier 201 of the first embodiment directly measures the voltage of the saturable reactor 106 (the rectifier 200 of the first comparative embodiment indirectly measures the voltage of the saturable reactor 106 by measuring the control current 114). Therefore, even if the "relationship between the control current 114 and the output voltage of the diode rectifier 103" changes as shown in FIG. 4, no error occurs, as in the first comparative embodiment. The operating points of the tap up command and tap down command only need to be set once in a factory test, and no adjustment of the operating points is required during actual operation. In other words, the intended number of tap changer switching operations can be ensured even during actual operation, reducing the possibility of shortening the life of the tap changer.

[0065] 5, the voltage detector 152 may have a surge absorption circuit that suppresses surges occurring in the burden voltage of the saturable reactor 106. This makes it possible to suppress the occurrence of circuit failures due to surges occurring in the burden voltage of the saturable reactor 106.

[0066] When the "relationship between the control current 114 and the output voltage of the diode rectifier 103" changes significantly, as in the characteristic C1 shown in Figure 4, the control current 114 supplied by the thyristor rectifier 143 in the first comparative example cannot fully utilize the voltage bearing capacity of the saturable reactor 106. In order to fully utilize the voltage bearing capacity of the saturable reactor 106, a bias circuit is required. However, because the programmable power supply 151 of the first embodiment can supply positive and negative currents, it is possible to fully utilize the voltage bearing capacity of the saturable reactor 106 even when the "relationship between the control current 114 and the output voltage of the diode rectifier 103" changes significantly, as in the characteristic C1.

[0067] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

[0068] The rectifier device according to the above embodiment can be applied to a transformer rectifier (power supply device) used to supply power to a refining process for non-ferrous metals such as aluminum, copper, and zinc, and for refining caustic soda, for example. [Explanation of symbols]

[0069] 101 Voltage Regulating Transformer 101a Tap 101b Tap changer 102 Rectifier transformer 103 Diode Rectifier 104 VCR system 105 Direct current transformer (DCCT) 106 Saturable reactor 107 Wiring bus bar 112 Current setting value 114 Control Current 115 Bias control circuit 116 Bias Current 121 Tap changer control device 122 Tap change signal 123 Control current measurement signal 131 Automatic Current Control Device (ACR) 132 Control Signals 141 DC reactor 142 Flow divider 143 Thyristor Rectifier 144 Tapped Single-Phase Transformer 145 DC reactor 146 Diode Rectifier 147 Slider 148 Control Winding 151 Programmable Power Supply 152 Voltage detector 153 Measurement Signal

Claims

1. a first transformer equipped with a tap changer for changing taps; a second transformer to which the output of the first transformer is input; a wiring bus bar through which an output current of the second transformer passes; a diode rectifier connected to the wiring bus bar; a saturable reactor disposed between the second transformer and the diode rectifier, the saturable reactor being passed through by the wiring bus bar; a power supply that supplies a control current to a control winding wound around the saturable reactor; a detector for detecting a voltage generated in the control winding; a control device that switches the tap in accordance with the detected value of the voltage.

2. The rectifier according to claim 1 , wherein the control device switches the taps depending on the magnitude of the voltage.

3. 2. The rectifier device according to claim 1, wherein the detector detects a voltage between a first detection point before the control winding is wound around the saturable reactor and a second detection point after the control winding is wound around the saturable reactor.

4. The rectifier device according to claim 1 , wherein the power supply is a power supply capable of supplying positive and negative control currents to the control winding.

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