Voltage regulator, and voltage regulation method

Abstract

To suppress sudden voltage fluctuations when switching taps.SOLUTION: A voltage regulator 10 comprises a transformer 20 and a regulation power supply 40. The transformer 20 comprises primary windings 21, secondary windings 22, and taps 25 disposed in one of the primary windings 21 and the secondary windings 22. The regulation power supply 40 is an inverter 41 connected in series to the primary windings 21 and the secondary windings 22.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for regulating voltage. [Background technology]

[0002] One type of power distribution equipment is a voltage regulator. Patent Document 1 discloses that voltage is adjusted by changing the tap of a transformer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-19310 Summary of the Invention [Problem to be solved by the invention]

[0004] A transformer with a tap adjusts the voltage in stages, and when the tap is changed, the voltage fluctuates suddenly. [Means for solving the problem]

[0005] The voltage regulator includes a transformer having a primary winding, a secondary winding, and a tap disposed on either the primary winding or the secondary winding, and the regulated power supply is an inverter connected in series with the primary winding or the secondary winding. Effect of the Invention

[0006] It allows for continuous voltage adjustment and smooths out voltage fluctuations during tap changing. [Brief description of the drawings]

[0007] [Figure 1] Voltage regulator circuit diagram [Diagram 2] Voltage regulator circuit diagram [Diagram 3]Voltage Regulator Equivalent Circuit [Figure 4] Voltage regulator circuit diagram [Diagram 5] Voltage regulator circuit diagram [Figure 6] Voltage regulator circuit diagram [Figure 7] Voltage regulator circuit diagram [Figure 8] Voltage Regulator Control Circuit [Figure 9] Graph showing the simulation results [Figure 10] Graph showing the simulation results [Figure 11] Diagram showing voltage changes during tap changing [Figure 12] Amplitude command block diagram [Figure 13] Graph showing the simulation results [Figure 14] Graph showing the simulation results [Figure 15] Block diagram of consumer system [Figure 16] Voltage Regulator Control Circuit [Figure 17] Graph showing the simulation results [Figure 18] Graph showing the simulation results [Figure 19] Voltage regulator circuit diagram DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (Outline of this embodiment) (1) A voltage regulator according to one embodiment of the present invention includes a transformer and a regulated power supply. The transformer includes a primary winding, a secondary winding, and a tap installed on either the primary winding or the secondary winding. The regulated power supply is an inverter connected in series to the primary winding or the secondary winding.

[0009] According to the voltage regulator of the embodiment of the present invention, a voltage intermediate between the switching voltages of the taps can be output by the inverter, and the voltage can be continuously adjusted, so that the voltage fluctuations at the time of tap switching can be smoothed out.

[0010] (2) In the voltage regulating device described in (1) above, the inverter may execute cooperative control to smooth fluctuations in the load voltage during tap changing. By executing cooperative control, it is possible to mitigate abrupt fluctuations in the load voltage during tap changing.

[0011] (3) The voltage regulator according to (1) or (2) above may further include a control circuit that feedback controls the amplitude of the load voltage to an amplitude command value, and an amplitude command unit that outputs the command value of the amplitude of the load voltage to the control circuit. The amplitude command unit may include an amplitude detector that detects the amplitude of the secondary voltage of the transformer, and a first-order lag filter that outputs a first-order lag signal of the detection signal of the amplitude detector as the command value of the amplitude of the load voltage. Since the load voltage is adjusted to the first-order lag voltage of the secondary voltage of the transformer, it is possible to mitigate abrupt voltage fluctuations in the load voltage at the time of tap changing and to smooth the voltage fluctuations.

[0012] <Embodiment 1> 1. Description of Voltage Regulator 10 Fig. 1 is a circuit diagram of a voltage regulator 10. The voltage regulator 10 disclosed in Fig. 1 is composed of a three-phase transformer 20U, 20V, 20W, and a three-phase regulated power supply 40.

[0013] The transformers 20U, 20V, and 20W include primary windings 21U, 21V, and 21W, secondary windings 22u, 22v, and 22w, and taps 25U, 25V, and 25W. The primary windings 21U, 21V, and 21W are connected to an AC power source (not shown), and the secondary windings 22u, 22v, and 22w are connected to a load R.

[0014] The taps 25U, 25V, and 25W change the winding ratio n of the primary windings 21U, 21V, and 21W and the secondary windings 22u, 22v, and 22w. In this example, the taps 25U, 25V, and 25W are provided on the primary windings 21U, 21V, and 21W.

[0015] The regulated power supply 40 is connected in series to the secondary windings 22u, 22v, and 22w. The regulated power supply 40 is a three-phase inverter 41, as shown in FIG.

[0016] The three-phase inverter 41 converts the DC voltage of a DC power supply into a three-phase voltage and outputs it, and is capable of continuously adjusting the voltage by PWM control. The DC power supply of the three-phase inverter 41 may be a capacitor or a secondary battery.

[0017] 3 is an equivalent circuit of the voltage regulator 10. As shown in Equation 1, the load voltage VL is the sum of the secondary voltage V2 of the secondary winding 22 and the output voltage Vinv of the three-phase inverter 41, and stepwise voltage adjustment by the tap 25 (first item on the right side) and continuous voltage adjustment by the three-phase inverter 41 (second item on the right side) are possible.

[0018] VL = V2 + Vinv (1)

[0019] In the following description, the primary windings 21U, 21V, and 21W are collectively referred to as the primary winding 21, and the secondary windings 22u, 22v, and 22w are collectively referred to as the secondary winding 22. In addition, the taps 25U, 25V, and 25W are collectively referred to as the taps 25.

[0020] 1 and 2, as an example of the voltage regulator 10, the tap 25 is provided on the primary side of the transformer 20, and the three-phase inverter 41 is provided on the secondary side. The arrangement of the tap 25 and the three-phase inverter 41 is not limited to the above example, and the tap 25 may be provided on the secondary side of the transformer 20, and the three-phase inverter 41 may be provided on the primary side of the transformer 20, as shown in FIG.

[0021] 5, the tap 25 and the three-phase inverter 41 may be installed on the primary side of the transformer 20, or as shown in Fig. 6, the tap 25 and the three-phase inverter 41 may be installed on the secondary side of the transformer 20. The connection of the transformer 20 is not limited to the YY connection, and may be a Δ-Y connection, a Y-Δ connection, or a Δ-Δ connection.

[0022] 7 adds a capacitor C to the voltage regulator 10 shown in FIG 1. The capacitor C is disposed between the three-phase lines, and constitutes an LC filter together with an inductance L provided in the output stage of the three-phase inverter 41. The LC filter makes it possible to suppress switching noise of the three-phase inverter 41.

[0023] 8 shows a control circuit 50A of the voltage regulator 10. The control circuit 50A includes a DC voltage compensator 51, a three-phase command generator 53, a voltage compensator 55, and a PWM signal generator 57. In order to keep the DC voltage Vdc of the three-phase inverter 41 constant, the DC voltage compensator 51 feeds back Vdc and outputs to the three-phase command generator 53 a phase signal and / or an amplitude signal such that the DC voltage Vdc coincides with a command value Vdcref.

[0024] The three-phase command generator 53 receives the signal output from the DC voltage compensator 51 and the amplitude command value V Lref and the power supply voltage V 1U , V 1V , V 1W Based on the detection value of the AC power supply voltage V 1U , V 1V , V 1W The amplitude command value V of the load voltage VL is synchronized with Lref The device outputs a voltage signal (three-phase AC signal) corresponding to the

[0025] The voltage compensator 55 receives the three-phase load voltage V LU , V LV , V LWBased on this feedback signal and the voltage signal of the three-phase command generator 53, the control signal is output to the PWM signal generator 57 so that the amplitude of the load voltage VL coincides with the amplitude command value VLref.

[0026] In this way, the control circuit 50 can feedback control the amplitude of the load voltage VL to the amplitude command value VLref by adjusting the output voltage of the three-phase inverter 41.

[0027] 9 shows the results of simulating the fluctuation of the load voltage VL when the secondary voltage V2 of the transformer 20 is changed. The simulation conditions are as follows, and the secondary voltage V2 of the transformer 20 is switched at time t1 in FIG.

[0028] V2: 200V⇒100V VL (command value): 200V Load R: 75 Ω, inductor L: none

[0029] As a result of the simulation, even if the secondary voltage V2 of the transformer 20 changes stepwise due to tap switching, the amplitude of the load voltage VL is kept roughly constant, confirming the effectiveness of the control circuit 50 (effectiveness of the feedback control).

[0030] Fig. 10 shows the results of simulating the fluctuation of the load voltage VL when the power supply voltage of the AC power supply contains harmonics, and the harmonics are superimposed on the power supply voltage at time t1 in Fig. 10. As shown in Fig. 10, the harmonic components are compensated for by adjusting the output voltage of the three-phase inverter 41, so that the load voltage VL can be made to be approximately a sine wave.

[0031] 11 is a diagram showing voltage changes during tap switching. In this example, the secondary voltage V2 of the transformer 20 changes (drops) stepwise at time t1, and the secondary voltage V2 of the transformer 20 changes (rises) stepwise at time t2.

[0032] 12 is a block diagram of the amplitude command unit 70. The amplitude command unit 70 is made up of an amplitude detector 71 that detects the amplitude of the secondary voltage V2 of the transformer 20, and a first-order lag filter 73. The amplitude command unit 70 outputs a signal, which is generated by passing the detected value of the secondary voltage V2 of the transformer 20 through the first-order lag filter 73, to the three-phase command generator 53 of the control circuit 50A as an amplitude command value VLref of the load voltage VL.

[0033] As a result, at the time of tap changing, the amplitude of the load voltage VL is adjusted (cooperative control) by the three-phase inverter 41 to the first-order lag voltage of the secondary voltage V2 of the transformer 20, so that abrupt voltage fluctuations in the load voltage VL at the time of tap changing can be mitigated and the voltage fluctuations can be smoothed out (part A in FIG. 11). Note that cooperative control refers to controlling the three-phase inverter 41 and the tap changing operation in cooperation with each other in order to smooth out fluctuations in the load voltage VL at the time of tap changing.

[0034] 13 and 14 show the results of simulating the fluctuation of the load current IL at the time of tap changing in the cases without and with coordinated control by the three-phase inverter 41. The simulation conditions are as follows.

[0035] Before the tap change, V2 = VL = 100V. Change V2 from 100V to 150V by tap changing. The load R is a capacitor-input rectifier.

[0036] As shown in Fig. 13, when there is no coordinated control of the three-phase inverter 41, an excessive switching current (part B) flows through the load R at the time of tap switching. As shown in Fig. 14, when there is coordinated control of the three-phase inverter 41, it is possible to prevent an excessive switching current from flowing through the load R.

[0037] 2. Application Examples of the Voltage Regulator 10 15 is a block diagram of a customer system S1. The customer system S1 is connected to a power system 1. The power system 1 is a system operated by an electric utility company, and has a three-phase system power source 3.

[0038] The customer system S1 includes a voltage regulating device 10, a plurality of load equipments 110 to 130, and a controller 150. The first load equipment 110 and the second load equipment 120 are AC loads, and the third load equipment 130 is a DC load.

[0039] The controller 150 is communicably connected to each of the load equipment 110-130, and communicates various information with each of the load equipment 110-130.

[0040] The communicated information includes information about the operating state of each of the load equipment 110 to 130 (for example, the rotation speed of the motor, etc.).

[0041] The controller 150 controls the voltage regulating device 10 based on the operating state of each of the load facilities 110 to 130, thereby controlling the distribution voltage Vin of the customer system S1 to an optimal value.

[0042] 3.Effects The voltage regulator 10 according to the first embodiment uses both the transformer 20 and the three-phase inverter 41, and therefore can output an intermediate voltage between the switching voltages of the tap 25 by the three-phase inverter 41, enabling continuous voltage regulation. This makes it possible to mitigate sudden fluctuations in the load voltage VL at the time of tap switching. Furthermore, compared to a case where the voltage regulator 10 is configured with only the three-phase inverter 41, it is possible to use an inverter 41 with a smaller capacity, which has a cost advantage.

[0043] <Embodiment 2> Fig. 16 is a block diagram of a control circuit 50B of the voltage regulator 10. The control circuit 50B disclosed in Fig. 16 differs from the control circuit 50A disclosed in Fig. 8 in that a high-pass filter 61 and a current compensator 63 are added.

[0044] The high-pass filter 61 suppresses low-frequency components from the load current IL detected by the current detector and passes only high-frequency components. Note that iLuh*, iLvh*, and iLwh* in Fig. 16 are output signals of the high-pass filter (harmonic components of the load current IL).

[0045] A signal obtained by subtracting the output signal of the high-pass filter 61 from the signal output from the voltage compensator 55 is input to the current compensator 63 .

[0046] Based on the input signal, the current compensator 63 outputs a control signal (command value) to the PWM signal generator 57 so that the amplitude of the load voltage VL coincides with the amplitude command value VLref and the harmonic components of the load current IL are suppressed. Note that the harmonic suppression control refers to control that suppresses the harmonic components of the load current IL by feeding back the harmonic components of the load current IL and correcting the command value for the PWM signal generator 57 with the current compensator 63.

[0047] 17 and 18 show the results of simulating the change in the load current IL during tap changing with and without harmonic suppression control.

[0048] As shown in Fig. 17, when harmonic suppression control is not performed, spike-like distortion occurs in the load current IL. As shown in Fig. 18, when harmonic suppression control is performed, the edges of the load current IL change to a rounded shape, and the spike-like distortion is alleviated.

[0049] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0050] (1) In the first embodiment, an example is shown in which the voltage regulator 10 regulates the distribution voltage Vin of the consumer, but the use of the voltage regulator 10 is not limited to regulating the distribution voltage Vin. The voltage regulator 10 can be appropriately applied to any purpose for voltage regulation.

[0051] (2) In the first embodiment, the voltage regulator 10 is for three phases. However, as shown in FIG. 19, it is also possible to use the voltage regulator 10 for a single phase.

[0052] (3) In the first embodiment, in the cooperative control by the three-phase inverter 41, the command value of the amplitude of the load voltage VL is controlled using the first-order lag filter 73. The amplitude of the load voltage VL may be controlled by another method as long as the method smoothes the fluctuation of the load voltage VL during tap changing. [Explanation of symbols]

[0053] 10. Voltage Regulator 20. Transformer 21 Primary Winding 22 Secondary Winding 25 Taps 41 Inverter 50A, 50B Control circuit 70 Amplitude command section 71 Amplitude Detector 73 First-order lag filter

Claims

1. 1. A voltage regulator comprising: Transformer and a regulated power supply; The transformer is A primary winding; A secondary winding; a tap disposed on either the primary winding or the secondary winding; A voltage regulating device, wherein the regulated power supply is an inverter connected in series with the primary winding or the secondary winding.

2. 2. The voltage regulator of claim 1, The inverter is a voltage regulator that performs coordinated control during tap changing to smooth out fluctuations in the load voltage.

3. 3. The voltage regulator according to claim 1 or 2, A control circuit that feedback controls the amplitude of the load voltage to an amplitude command value; an amplitude command unit that outputs a load voltage amplitude command value to the control circuit; The amplitude command unit is an amplitude detector for detecting an amplitude of a secondary voltage of the transformer; a first-order lag filter that outputs a first-order lag signal of the detection signal from the amplitude detector as a command value for the amplitude of a load voltage.

4. 1. A method for regulating voltage, comprising: A voltage regulation method that smooths out fluctuations in the load voltage by changing the output voltage of an inverter connected in series to the primary or secondary winding of a transformer when changing taps.

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