KR200337331Y1 - High Voltage Constant Voltage Control Device Using Transformer Parallel Connection - Google Patents

Abstract

In Korea, the frequency used in the power system is 60Hz. This is called the commercial frequency. Controlling the voltage at the commercial frequency means controlling the magnitude and frequency of the voltage.

In general, it is not technically easy to control the voltage at the commercial frequency because it is difficult to control the voltage at the commercial frequency because the high voltage and high energy power. Nevertheless, constant high-quality constant voltage that is constant in frequency and unstable in size is required not only in the field of precision electrical equipment, especially in the field of using motors, but also in the recent precision information and communication business. In addition, if the voltage fluctuation rate is severe, the life of the electric device is shortened and the brightness of the lamp is shaken, which causes inconvenience in daily life.

The voltage control method currently used in power system or high voltage and high power field includes inverter type, manual voltage changer of power distribution transformer, and automatic tap changer used in ultra high voltage transformer, which is complicated in controller, expensive in device, large in size, Difficulty in controlling and inducing action in the controller causes various problems.

In order to solve the above problems and to enable a controller that does not affect the voltage quality, a high power constant voltage control device using a novel parallel transformer connection has been devised.

Description

High voltage constant voltage control device using transformer parallel connection

In Korea, the frequency used in the power system is 60Hz. This is called the commercial frequency. Controlling the voltage at the commercial frequency means controlling the magnitude and frequency of the voltage. In general, it is difficult to control the voltage at the commercial frequency because the control of the voltage at the commercial frequency is not easy. Nevertheless, constant high-quality constant voltage that is constant in frequency and unstable in size is required not only in the field of precision electrical equipment, especially in the field of using motors, but also in the recent precision information and communication business. In addition, if the voltage fluctuation rate is severe, the life of the electric device is shortened and the brightness of the lamp is shaken.

The current high voltage power system or high voltage field will be explained in three ways.

First, control by the inverter method mainly used in a single device (FIG. 2)

Second, the first manual tap switching method used in the distribution transformer (FIG. 3)

Third, automatic tap switching device used in the substations of ultra high pressure large capacity (FIG. 4)

With the development of power semiconductor devices, that is, power electronic devices, the most common device of voltage control has become an inverter-based system (Fig. 2). Inverter voltage control technology is to rectify AC voltage into DC voltage, and then make AC again by switching the power electronic device. The operating principle of the voltage controller in this manner is to rectify the power supply (4 in Fig. 2) and make a DC waveform, and then go through a filter 23 to make a high-quality DC power supply, and then the power device (Fig. 2). Qp1, Qp2, Qn1, and Qn2) are controlled by the gate controller 26 to drive the inverter 24 to generate alternating current, and the filter 25 is again used to make the alternating voltage signal again to make a cleaner AC voltage. After rough supply to the load (3 in Figure 2).

Advantages of the voltage control method of the inverter method of FIG. 2 are largely as follows.

First, it can control even frequency

Second, the wide voltage control range

Instead of having the advantages of the inverter type control that uses the power electronic device to control the voltage has the following disadvantages.

First, the controller is complicated and the device (Qp1, Qp2, Qn1, Qn2 in FIG. 2) becomes expensive. In particular, in the case of a large capacity of several tens of kVA or more, the price of reactors (L1 and L2 in FIG. 2) and capacitors (C1 and C2 in FIG. 2) used to smooth the price of the device may be several hundred thousand won.

Second, control is difficult. Accurate control is necessary to maintain the correct voltage and frequency. This gate controller 26 is usually controlled by a microprocessor.

Third, the voltage control by the inverter controller (FIG. 2) is basically a device that uses the switching action of the power electronic device (Qp1, Qp2, Qn1, Qn2 in FIG. 2), a lot of high frequency and harmonics are generated during the switch operation. The generation of such harmonics causes an induction effect on a communication facility.

Fourth, a lot of heat is generated. The voltage control by the inverter controller (Fig. 2) is basically a device that uses the switching action of the power electronic device (Qp1, Qp2, Qn1, Qn2 in Fig. 2) generates heat by switching during the operation of the switch. Usually heatsinks and cooling fans are attached to suppress this heat. Heat is power dissipation and cooling fan is power dissipation.

Fifth, the higher the capacity, the more expensive. Currently, voltage control by power electronics is widely used in a single electric device, for example, an electric device using a small motor, and it is small in size and low in price. However, power devices using power of several tens of kVA are very expensive and difficult to control. However, even though it is expensive, it is being used in some necessary places, but it is not widely used for large-capacity voltage control, and especially for voltage control in power system, it is currently almost impossible to use due to price, harmonic and high frequency problems.

The voltage system used to supply a constant voltage to the consumer in the power system is largely divided into the voltage control method (Fig. 4) used in the substation unit and the voltage control method used in the distribution transformer or column transformer (Fig. 3). The voltage method used in the substation unit is a method that can control the voltage even while supplying power, and the power is more than several hundred kVA, and the method used in the distribution transformer requires a power failure operation to change the voltage. kVA or less.

First, the voltage control method of the distribution transformer will be described. 3 is a voltage control method used in a column transformer or a column transformer. In FIG. 3, the power supply voltages 4 and 32 of FIG. 3 are voltages provided by the large transformer of the substation. The voltage control method in the distribution transformer is a method of manually converting and winding the windings on the primary side of the distribution transformer.

Multiple taps (34 in FIG. 3) are mechanically fed to the primary winding 36 of the distribution transformer or columnar transformer 33 to change the winding ratio of the transformer primary side to change the voltage of the transformer secondary winding 27 (Fig. 3). 5) change the way. If the direction of the primary winding is the L direction of FIG. 3, the secondary voltage of the distribution transformer (5 in FIG. 3) is lowered. On the contrary, if the direction of the primary winding is the H direction of FIG. 3, the secondary voltage of the distribution transformer (5 of FIG. 3) is decreased. ) Increases.

This type of voltage control method is called a tap-changing method, and is generally the most commonly used in distribution transformers. However, there are three problems with this approach.

First, an electrostatic work is required to transfer the tab 34 on the primary side mounted on the power distribution transformer 33. Therefore, voltage control cannot be performed while supplying voltage to the customer. It causes the inconvenience of power failure during the tap change operation.

Second, there is a risk factor in switching the primary side tap of the distribution transformer 33. In other words, it is dangerous because a person must work by using an air hole.

Third, when the load (3 in FIG. 3) is connected when a certain tap is connected, and the current flowing through the load changes, the load terminal voltage (5 in FIG. 3) is not constant. In other words, the voltage changes according to the load, so that the constant voltage cannot be supplied to the load (3 in FIG. 3).

In order to supply a constant voltage to the load (3 in Fig. 3) stage in the columnar transformer 33, an effort to improve the above three disadvantages is required.

Another device for controlling the voltage used in the power system is a device by an automatic load switching device (Fig. 4) of the load state. It is installed in substations, has a voltage of several hundred kV, and power is used in ultra high voltage high power transformer for tens of MVA.

In this method, a plurality of taps are formed by connecting a lead wire to the middle of the winding of the secondary winding 43 of the ultra-high voltage transformer, which receives the voltage generated by the power plant as the primary side voltage 41 and modifies the voltage. It is a method of automatically adjusting by electric gear.

There are two main advantages to this approach:

First, the voltage can be adjusted while supplying power so that no power failure occurs.

Second, there is no risk when operating because it is automatically controlled.

But there are disadvantages to this approach.

First, the number of taps present in the OLTC on the secondary side of the ultra-high voltage transformer 44 is about 20 steps, not a continuous voltage control method.

Second, it is expensive. It is an expensive power device that costs about tens of percent of the ultra high voltage transformer 44.

Third, the size, that is, the size is very large. Therefore, it is unreasonable to apply this voltage method to the secondary side of the distribution transformer 33. The price is also high, which is tens of times the price of a distribution transformer.

At present, this is the most representative voltage control method used worldwide in substations. It is technically and economically impossible to control this method using pure power electronics.

As the voltage control method currently used in the power system or high voltage and high power field, an inverter method (FIG. 2), a distribution transformer manual tap switching method (FIG. 3), and an automatic tap changer (FIG. 4) used in the ultra-high voltage transformer 44 are provided. As a device to compensate for the shortcomings have been conceived under the following conditions.

First, the voltage must be controlled automatically.

Second, the structure should be simple and easy to handle.

Third, the price should be cheap and lightweight.

Fourth, it should not harm the voltage quality.

In the present invention, the following phenomenon was found to enable a controller that satisfies the above conditions. In general, the voltage fluctuation is not large in the voltage used in the power system or high voltage. For example, the rated voltage supplied to domestic households is 220V. At present, in the power system of Korea, the voltage of 220V falls within 5% even if the fluctuation is large. In other words, the voltage fluctuation range is small. Therefore, the width of the voltage to be controlled is not large. In this principle, it is not necessary to generate all the required power capacity like the inverter method.

In general, the transformer is connected in parallel with the power supply to change the voltage. 5 illustrates a general transformer 51 connection diagram. When several transformers are operated, that is, transformer parallel operation. As shown in FIG. 5, a transformer having the same characteristics is connected to a terminal of an input side in parallel, and a load (3 in FIG. 5) is applied to a secondary side to use a transformer. In other words, it is used in parallel with the load.

However, when one more transformer is used in series with this load (3 in FIG. 5), as shown in FIG. 6, the transformer is connected in series with the load. In FIG. 6, the transformer 51 may be applied to a distribution transformer, an ultra high voltage transformer, or a general transformer used in a consumer. In FIG. 5, the transformer 51 and the load (3 of FIG. 5) are connected in parallel. In this connection, the control transformer 56 is connected in series with the load 3 between the load (3 in FIG. 6) and the transformer (51 in FIG. 6). And the secondary switch 57 which is generally used is connected to the secondary side. In this state, when the load current (6 in FIG. 6) is kept constant and the contact switch 57 is closed and it is heated, the primary side voltage Vc of the control transformer 56 and the load terminal terminal voltage VL, FIG. Measure 6, 5). The phenomenon at this time is as follows.

First, when the contact switch 57 is opened, most of the voltage (Vt) supplied from the transformer (T1, 51 in Fig. 6) is applied to the control transformer primary side (Vc, 56), the load end voltage (VL, Fig. 6, 5) is very small. At this time, the current cannot flow in the secondary side of the control transformer 56.

Second, when the contact switch 67 is closed, most of the voltage (Vt) supplied from the transformer (T1, 51 in Fig. 6) becomes the load terminal voltage (VL, 5 in Fig. 6), the control transformer primary side ( Vc, 58) hardly takes voltage. At this time, a current inversely proportional to the transformer ratio of the control transformer 56 flows through the switch on the secondary side of the control transformer 56.

These test results can be concluded as follows.

First, when the control transformer 56 is connected in series with the load (3 in FIG. 6), the load terminal voltage (5 in FIG. 6) can be controlled. As a result, the voltage on the primary side of the control transformer changes according to the current on the secondary side of the control transformer 56.

Second, if the current on the secondary side of the control transformer 56 is controlled, the load terminal voltage VL (5 in FIG. 6) can be largely controlled. However, in order to control the load terminal voltage VL (5 of FIG. 6) in a large width, the capacity of the control transformer must be equal to the capacity of the general transformer 51. In other words, to increase the control width of the voltage, the capacity of the control transformer must be increased. However, in general, it is concluded that the capacity of the control transformer is minimal since the voltage fluctuations are not large in the power system. That is, if the variation range of the voltage to be controlled is 10%, the capacity of the control transformer 56 is 10% of the capacity of the general transformer (51 in FIG. 6). Therefore, the important conclusion is that a small transformer can control a large voltage. These phenomena and experimental results are the focus of the present invention.

Here, the apparatus for conveniently controlling the secondary side current 77 of the control transformer 56 of FIG. 1 is as follows. The target of the constant voltage control is the load terminal voltage (5 in FIG. 1). That is, even if the power source (71 in FIG. 1) is changed or the load (3 in FIG. 1) is changed so that the load current (6 in FIG. 1) is changed, the load terminal voltage (5 in FIG. 1) is constant. do.

If the load stage voltage (5 in Fig. 1) becomes large due to any cause, the control transformer primary voltage drop (58 in Fig. 1) is increased to decrease the load stage voltage and keep it constant. When 5) is small, the control transformer primary side voltage drop (58 in FIG. 1) is also small, so that the load terminal voltage (5 in FIG. 1) can be kept constant. Such a device is an idea of the present invention, and for this operation, a general transformer is connected in series with a load (3 in FIG. 1) and used as a control transformer (56 in FIG. 1).

Referring to the apparatus for making the load stage voltage (5 in FIG. 1) constant, when the load stage voltage (5 in FIG. 1) increases, the control transformer primary side voltage (58 in FIG. 1) is increased to increase the load stage voltage (FIG. 1). You can keep it constant by lowering 5). When the load stage voltage (5 in FIG. 1) decreases, the control transformer primary side voltage (58 in FIG. 1) may be decreased to increase the load stage voltage (5 in FIG. 1) and keep it constant. As a result, in order to keep the load stage voltage (5 in FIG. 1) constant, it is possible to increase or decrease the primary voltage (58 in FIG. 1) of the control transformer (56 in FIG. 1), and increase or decrease the control transformer (56 in FIG. 1). This can be done by increasing or decreasing the control transformer secondary current (77 in FIG. 1). In other words, to increase the control transformer primary side voltage (58 in FIG. 1), the secondary side current (77 in FIG. 1) of the control transformer may be decreased, and to reduce the primary side voltage (58 in FIG. 1) of the control transformer. It is sufficient to increase the control transformer secondary side current (77 in FIG. 1).

As a result, in order to constantly control the load terminal voltage VL (5 in FIG. 1), which is the control target voltage, the secondary side current Ic2 (77 in FIG. 1) of the control transformer may be increased or decreased. Therefore, controlling the control transformer 56 secondary side current Ic2 (77 in Fig. 1) leads to the conclusion that the load stage constant voltage control becomes the voltage control.

The apparatus for controlling the secondary side current Ic2 (77 in FIG. 1) of the control transformer to be controlled will now be described. For this purpose, a combination of three devices is used.

First, a plurality of taps (S1, S3, S4, and S5 in FIG. 1) are provided on the secondary side of a control transformer (56 in FIG. 1) connected in series with a load so that the magnitude of the voltage induced in the secondary side can be changed. . The adjustment of this tap was made so that the power electronic switch part (73 of FIG. 1) for tap control could be performed to perform "on" and "off" control.

Second, a capacitor group (74 in FIG. 1) used as a load was provided so that each of the capacitors could be individually controlled. Here, condenser control is performed in two ways. One device is a control part (75 in FIG. 1) that performs only 'on' and 'off' control, and each capacitor is connected to a load to operate at each capacity, and the other device is phase control (Fig. 11). The capacitor control phase control power electronic switch unit 76 can control the capacitor capacity finely. This allows the control transformer secondary currents to work smoothly rather than stepwise.

Third, a boost transformer is used as the control transformer 56. That is, the transformer 78 uses a transformer whose voltage 78 on the secondary side of the control transformer is higher than the voltage on the primary side. By doing so, the current 77 on the secondary side is small, the size of the power electronic device is small, less heat is generated, and the price is low.

A condenser 74 was used as a load for increasing and decreasing the secondary current (77 in FIG. 1) of the control transformer (56 in FIG. 1). The reason for using the capacitor 74 is that it has the following three advantages.

First, the capacitor 74 acts capacitively and therefore does not consume power.

Second, loads generally used in power systems are inductive and therefore have an effect of improving power factor.

Third, since the surge invading the primary side of the control transformer 56 passes through the control transformer 56 easily, the secondary capacitor condenser 74 absorbs it and blocks the surge from entering the load, thereby protecting the load stage. have.

The purpose of the present invention is to maintain a constant voltage across the load stage.

First, the hardware structure will be described in FIG. The secondary side current (77 in FIG. 7) of the control transformer (56 in FIG. 7) must be controlled in order to constantly control the load terminal voltage (5 in FIG. 7) which is the purpose of this voltage controller. For this control, four analog information are taken into the main controller (87 in Fig. 7).

First, a converter (88 in FIG. 7) for reading the power supply voltage Vac (71 in FIG. 7) into the controller 87.

Second, a converter (89 in FIG. 7) for reading the load terminal voltage VL (5 in FIG. 7) into the controller 87.

Third, a converter (90 in FIG. 7) for reading the control transformer secondary voltage Vc2 (78 in FIG. 7) into the controller 87.

Fourth, a converter (91 in FIG. 7) for reading the control transformer secondary current Ic2 (77 in FIG. 7) into the controller 87.

The above four pieces of information necessary for the constant voltage control are transmitted to the main controller (87 in FIG. 7) and used for signal generation for the following four parts.

First, when there is a problem in the main controller 87 or when the secondary side of the voltage control transformer (56 in FIG. 7) is opened, a 1-bit controller (FIG. 7) that operates the protective contact 72 to 'CLOSE' the control transformer secondary side. 82) Signal Generation

Second, when there are a plurality of taps on the secondary side of the control transformer 56, signal generation of the controller (83 in Fig. 7) for controlling the switch group (73 in Fig. 7) for selecting each tap.

Third, among the capacitors connected to the control transformer (56 in Fig. 7) secondary side to increase or decrease the secondary current (77 in Fig. 7) to perform only 'ON', 'OFF' control (Fig. 10) Signal generation of the controller (84 of FIG. 7) controlling 75 of FIG.

Fourth, a condenser switch group (FIG. 7) which performs phase control (FIG. 11) among the condensers connected to the control transformer (56 in FIG. 7) secondary side to increase and decrease the secondary current (77 in FIG. 7) finely. Signal generation of the controller (86 in FIG. 7) controlling 76)

The following describes the software that enables this control. Algorithms for generating the four control signals mentioned above are performed in the main controller (87 in FIG. 7) and constitute a microprocessor.

To simplify the explanation of the algorithm, let's define a step here. In Fig. 1, the secondary side tabs of the control transformer (56 in Fig. 1) are four (S1, S3, S4, S5 in Fig. 1). Corresponding switches are Q1, Q2, Q3, and Q4 in FIG. 1 and the gates are G1, G2, G3, and G4.

In addition, the capacitor control power electronic switch unit 76 is Q5, Q6, Q7, Q8 in Fig. 1, and the corresponding gates are G5, G6, G7, G8.

There are Q9 switch and gates G9 and G10 of phase control method for precision control.

If the number of cases is made up of only the tap switch section (73 in Fig. 1) and the condenser switch section (74 in Fig. 1), the number is 16 in 4 x 4 = 16. Let's define it as a step.

As shown in Table 1 and FIG. 1, increasing the step decreases the control transformer secondary currents Ic2 and 77 and increases the control transformer primary voltages Vc and 58, thereby increasing the load stage voltage VL and FIG. 5) decreases. Since the opposite is true, the load terminal voltage (5 in FIG. 1) is controlled by the step.

In conclusion, in order to decrease the load terminal voltage (5 in FIG. 1), the control transformer 56 needs to increase the primary voltage, thereby increasing the step. In addition, in order to increase the load terminal voltage, it is necessary to reduce the primary voltage of the control transformer 56, thereby reducing the step. That is, the increase in the number of steps is a decrease in the load terminal voltage (5 in Fig. 1).

FIG. 8 is a flowchart of a control algorithm for controlling the load terminal voltage VL to a constant voltage in FIG. 1. When the master controller 87 starts operation, the step defined in the program (Table 1) is loaded from the memory, and the constant voltage value desired by the user is stored. Then, externally, the power supply voltage information (71 in FIG. 1), the load end voltage (VL), the secondary side voltage (78 in FIG. 1) of the control transformer (56 in FIG. 1), and the secondary side current of the control transformer (in FIG. 1). 77) is A / D converted. Compared with the load terminal voltage (5 in Fig. 1) and the constant voltage value desired by the user (V _LD in Fig. 8), if the load terminal voltage (5 in Fig. 1) is large, the step is increased and phase control is performed to precisely control the voltage. (76 in Fig. 1). On the contrary, if the load terminal voltage (5 in Fig. 1) is small, the step is lowered and phase control (76 in Fig. 1) is performed for precise control.

Here, the voltage control method basically varies the step to control the voltage drop of the transformer primary side by step. This makes precise control difficult because the voltage is controlled step by step. Such voltage control is performed by the switch unit (Figs. 1, 73 and 75). This control method is described in FIG. Here, the load is purely a resistive load. As shown in Figure 10 it acts like a pure switch.

Complementary to the voltage control step by step to perform the phase control (Fig. 11) in 76 of Figure 1 to change the step-change voltage to a linear (96). Phase control is explained in FIG. Here, too, the pure resistance load is explained. As shown in FIG. 11, the switching operation is performed in the phase of a specific part of the voltage waveform.

1 is a representative view of a constant voltage control device of the present invention

2 is a structural diagram for explaining an inverter which is a type of voltage control;

3 is an explanatory diagram of voltage control of a columnar transformer or a distribution transformer used in a power system;

4 is an explanatory diagram of voltage control of a large-capacity transformer used in a substation

5 is a general transformer connection diagram

6 is a diagram illustrating a voltage drop using a transformer

7 is a control diagram for explaining a constant voltage control device of the present invention

8 is a flowchart of a control algorithm for explaining the present invention.

9 is an explanatory diagram of a step and a control transformer primary voltage drop

10 is an explanatory diagram for switch control

[Description of the code for the main parts of the drawing]

1. 2. Terminal of load stage

It is the purpose of the constant voltage to constantly control the voltage applied between these two terminals. In addition, it is constant voltage control to make the voltage between these two terminals constant and to stabilize the frequency.

3. Load

It is generally a load from an electrical point of view. All electrical appliances and appliances used for home or industrial purposes are loads. The load is divided into resistive loads such as electric lamps (phase load) and inductive loads such as motors (ground load), discharge or condenser and capacitive loads (phase loads). Here, in-phase load means that the phase of voltage and current match, ground load means that it is 90 degrees late when the current is based on the phase of the voltage, and true load means 90 degrees when the current is referenced to the voltage. .

4. Power

Means the power supplied by the electricity provider. It means to supply infinite energy electrically, and that the internal impedance is '0' is called the ideal power source.

5. Load stage voltage

The voltage applied to the load 3 is referred to. In the present invention, the constant voltage control means to make the load stage voltage mentioned here constant. In the constant voltage control, the magnitude of the voltage applied to the load stage is constant and the frequency is constant. In this condition, the voltage magnitude and frequency are kept constant even when the characteristics of the load 3 are changed to resistive, capacitive and inductive. Say that.

6. Load current

Current supplied to the load (3)

22. Rectifier

This part converts AC power into DC power and consists of 4 rectifier element diodes. Another representation of the rectifier is called a converter. The circuit here is a full-wave rectifier circuit. Converting AC power to DC power is called rectification.

23 Smoothing Filter

The voltage waveform rectified in the rectifier 22 is a waveform having an AC component instead of a complete direct current. Such a waveform is referred to as 'having a pulsating component' and becomes a voltage waveform closer to direct current by the reactor (L1 in FIG. 2) and the condenser (C1 in FIG. 2).

24 inverter

The inverter part makes a voltage of a desired frequency and a desired magnitude again by the DC voltage passed through the smoothing filter. A new AC power supply is made by switching power electronic devices.

25 smoothing circuit

AC voltage made by using power electronics contains many harmonics and high frequencies, so when the harmonics and high frequencies are applied to the load, noise, communication disturbances, etc. occur. Therefore, a filter is used to limit these harmonics and high frequencies.

26 gate control circuit

The switch function of the power electronic device used in the inverter of the 24 corresponds to the part for controlling the voltage and frequency. Usually controlled by a microprocessor. In addition, by using an isolated power supply as a control power supply to ensure the operation of each power electronic device. However, it is expensive to manufacture such an isolated power supply.

31. Switching TAP

Multiple taps (34 in FIG. 3) are mechanically fed to the primary winding 36 of the distribution transformer or columnar transformer 33 to change the winding ratio of the transformer primary side to change the voltage of the transformer secondary winding 27 (Fig. 3). 5) to change.

32. Primary voltage of main transformer or distribution transformer

This voltage is the voltage supplied from the substation.

33. Distribution transformer or column transformer

It refers to a transformer that acts as a low-voltage transformer used by general consumers and at home by receiving power from substations connected to the power system. In Korea, the primary side voltage is 22.9 [kV] as the nominal line voltage, and the secondary side is the voltage supplied to the customer. The voltage is 220 [V].

34.TAP

In order to supply a constant voltage to a home or a general power customer, by making a plurality of connection points on the primary winding of the distribution transformer 33 and changing them manually, mechanical to maintain a constant voltage (5 in FIG. 3) on the secondary side, Electrical structure.

35. Tap (34) switching direction

When the tap is connected in the L direction of FIG. 3, the voltage on the secondary side of the distribution transformer 33 (5 in FIG. 3) decreases, and when the tap is connected in the H direction of FIG. 3, the voltage on the secondary side of the distribution transformer 33 (FIG. 5 of 3 rises.

36. Distribution transformer 33 primary winding

37. Secondary winding of distribution transformer 33

41. Primary voltage of the high voltage transformer 44 used in the substation

42. Primary winding of ultra-high voltage transformer 44

43. Secondary winding of ultra-high voltage transformer 44

44. Ultra high voltage transformer used in power system of substation

Primarily, the primary voltage is more than a few hundred kV and the capacity is tens of MVA, which is a large capacity transformer.

45. Automatic tap-changer

An on-load tap changer (OLTC) capable of performing tap switching in a state of supplying power to a tap installed on the secondary side of the ultra-high voltage transformer 44.

46. Secondary voltage of high voltage transformer

47. Secondary output terminal of high voltage transformer

This terminal is connected to the wire and used as the primary voltage of the distribution transformer 33.

51. Common Transformer

When several transformers are used as a general transformer, that is, a transformer to be operated in parallel uses a transformer having the same internal characteristics in parallel.

52. Primary terminal (P1) of the control transformer proposed in the present invention

53. Primary terminal (P2) of control transformer proposed in the present invention

54. Secondary terminal (S1) of the control transformer proposed in the present invention

55. Secondary terminal (S2) of the control transformer proposed in the present invention

56. Control Transformer

The voltage controlled transformer proposed in this invention is used in series with the load.

57. General contact switch

General switch for extreme testing of control transformer 56

58. Voltage Vc across the primary side of the control transformer 56.

71. Power

This power supply depends on the voltage to be controlled. If the control voltage is the secondary of the ultrahigh voltage transformer 44, the power supply becomes the primary voltage of the ultra high voltage transformer 44, and if the control voltage is the secondary side of the distribution transformer 33, the main power is the primary side of the distribution transformer 33. When the control voltage reaches the customer voltage, the power supply becomes the secondary voltage of the distribution transformer.

72. Mechanical relay 'b' contact

If an abnormality occurs in the controller due to mechanical contact, the controller returns to the 'b' contact to stop the operation of the control transformer (56 in FIG. 6).

73. Power electronic switch unit for tap control

A power electronic switch for controlling the secondary side current (77 in FIG. 1) of the control transformer (56 in FIG. 1) in a wide and detailed manner by drawing a plurality of tabs on the secondary side of the control transformer (56 in FIG. 1). Controlled by software This switch is only responsible for 'on' and 'off' control (Fig. 10).

74. Condenser Family

In order to control the primary voltage drop (58 in FIG. 1) of the control transformer (56 in FIG. 1), the secondary side current (77 in FIG. 1) of the control transformer should be controlled and used as a load for varying this current. There are two reasons for using a condenser as the load of the control transformer (56 in FIG. 1). In general, the load is inductive, so the power factor is improved and the resistive load is not a power consumption.

75. Power electronic switch unit for condenser control

The power electronic switch unit used to control the secondary side current 77 of the control transformer (56 in FIG. 1) by varying the capacity of the capacitor is responsible for only 'on' and 'off' control (FIG. 10).

76. Phase control power electronic switch unit for condenser control

Since the switch of 75 is only in charge of 'on' and 'off' control, the secondary side current (77 in FIG. 1) of the control transformer (56 in FIG. 1) is controlled in a stepped manner. A switch for realizing phase control (FIG. 11) so that such stepwise increase / decrease becomes as smooth as analog control.

77. Secondary Side Current of Control Transformer (56 in Fig. 1)

Controlling this current inversely changes the primary side voltage of the control transformer, i.e., the voltage drop (58 in Fig. 1). That is, Vc (58 in FIG. 1) may be controlled to make the load terminal voltage (5 in FIG. 1) constant where a constant voltage is required. In order to control Vc again, the control transformer secondary side current 77 may be controlled, and the secondary side current may be controlled by controlling the switches 73, 75, and 76 that control the capacitor 74.

78. Secondary voltage of control transformer (56 in Fig. 1)

In order to diversify the voltage, a plurality of taps were provided on the secondary side of the control transformer (56 in FIG. 1).

81. Current transformer

Current sensor for detecting secondary current of control transformer (56 in FIG. 7)

82. 1 bit controller to control protection contact

83. Controller for controlling the switch group (73 in Fig. 7) for switching the multiple taps on the secondary side of the control transformer

84. Control transformer Controller for controlling the switch group (75 in Fig. 7) for switching the capacitor used as the secondary load

86. Controller to control switch (76 in Fig. 7) for precise phase control by selecting one of several capacitors on the secondary side of control transformer

87. Main controller to control the whole system

88. Analog-to-digital converter digitally signaling the power supply voltage (71 in FIG. 7) to the main controller 87.

89. Analog-to-digital converter digitally converts the control transformer (56 in FIG. 7) to receive the primary voltage drop (58 in FIG. 7) as the main controller (87).

90. Analog-to-digital converter for digitally signaling the secondary side voltage (78 in FIG. 7) of the control transformer (56 in FIG. 7) to the main controller 87.

91. Analog-to-digital converter for digitally signaling the secondary side current (77 in FIG. 7) of the control transformer (56 in FIG. 7) to the main controller 87.

95. Primary voltage drop curve of control transformer for step with step and phase control

96. Part where primary voltage drop of control transformer is controlled by phase control

97. Part where the primary voltage drop of control transformer is controlled by 'on' and 'off' control of switch

.

Unlike the inverter method (Fig. 2) and the transformer tap adjustment method (Fig. 3) which make the existing AC power by switching operation of the power device in controlling the voltage used in the power system, the present invention is in series with the load. By connecting a commonly used transformer and controlling the current on the secondary side of the transformer, it has a structure that causes a voltage drop on the primary side of the transformer. The advantages of the voltage control scheme of this structure are as follows.

First, it can be used for voltage control for high power. In the case of a large power transformer, the device of the present invention can be applied because the width of the voltage to be controlled is not large. For example, if the voltage width to be controlled in the 10kVA, 220V supply transformer is 5%, the capacity of the control transformer used in the present invention is determined as follows.

If the control voltage width is 5% in the jdrur 220V, 10KVA load, the control voltage is 11 [V]. At maximum load, the current through the primary side of the control transformer is 45.45 [A]. Therefore, the capacity of the control transformer is about 500 [VA]. 5% of the supply transformer. That is, a small transformer of 500 [VA] is used for 5% voltage control of a large-capacity transformer of 10 kVA. The device is also available for hundreds of kVA. If the desired voltage control width is small, a compact and lightweight controller configuration is possible. At low voltages, a wide range of precise voltage control is possible.

Second, the desired constant voltage is automatically controlled. Devices currently used in power systems control mechanical contacts manually or automatically. Therefore, life and operating mechanisms are complicated. The present invention acts like a mechanical contact, but actually acts as a power electronic switch.

Third, the power factor is improved. The control transformer (56 in FIG. 1) used in this controller uses a condenser as the secondary side load, thereby improving the power factor. When described on an equivalent circuit, it works as if a capacitor is connected to the line.

Fourth, it does not impair power quality. In general, the inverter method (FIG. 2) and the automatic tap-changer (FIG. 3) are used to generate harmonics at an operation moment. In the case of the present design, since the classical transformer of the device is used, the power quality is not impaired. It also does not cause communication disturbances.

Fifth, low-cost, lightweight products are possible. In particular, when the voltage control width is small, the control transformer 56 also becomes small. In particular, by using the booster type control transformer 56, the secondary side has an advantage that the power electronic switch element can be used at low cost. This phenomenon is generally used power electronic switching device has a characteristic that withstands high voltage well, the low current is low. The characteristics of such a switching element and the control transformer of the present invention are well matched with the use of a boost type.

Sixth, expansion to three phases is easy. Since one line of single phase is controlled, it is easily applied to each of three phases, so it is easy to expand to three phases.

Seventh, there is an absorption effect of surge. If a surge occurs in the power supply stage, the capacitor absorbs the surge on the secondary side of the control transformer to prevent the surge from entering the load.

Eighth, since a constant voltage can be maintained in the load, there is a power saving effect when the supply is controlled at a somewhat lower voltage as long as there is no difficulty in the operation of the load.

Ninth, constant voltage can be supplied regardless of the nature of the load. Since the voltage drop uses a classic transformer, the load can be resistive such as a lamp, capacitive like an arc lamp, inductive like a motor, and constant voltage control in any load characteristics.

Claims (10)

In fact, the voltage control in the power system is focused on the fact that only the voltage control within a few% to 10% of the rated voltage is required, and commonly used boost transformer (hereinafter referred to as control transformer) in series with the load, In controlling the load voltage (5 in FIG. 1) in the power system constantly, paying attention to the fact that the voltage drop on the primary side of the control transformer changes when the current on the secondary side of the control transformer is controlled; A control transformer 56 using a load (3 in FIG. 1) and a general transformer as the control transformer (56 in FIG. 1), and tapping the control transformer; A condenser group (74 in FIG. 1) connected to the tap (S1, S3, S4, S5 in FIG. 1) as a load of the control transformer on the secondary side of the control transformer (56 in FIG. 1), A tap-change switch (73, 75 in FIG. 1), which is a power electronic device used to control the secondary side current (77 in FIG. 1) of the control transformer of the control transformer (56 in FIG. 1), Control transformer (56 in FIG. 1) Power electronic switch (76 in FIG. 1) as phase control switch for precise control of secondary current Constant voltage control device, characterized in that using The switch according to claim 1, wherein the tap-changing switches (73, 75) In constant control of the load stage voltage (5 in FIG. 1), the control transformer (56 in FIG. 1) is connected in series with the load and the transformer is controlled to increase or decrease the current on the transformer secondary side (77 in FIG. 1). A constant voltage control device which maintains a constant voltage (5 in FIG. 1) supplied to a load by controlling the voltage drop (58 in FIG. 1) on the primary side, The method of claim 1, The control transformer (56 in Fig. 1) uses the capacitor (74 in Fig. 1) having a function of compensating reactive power without consuming active power to the secondary load (74 in Fig. 1) (77 in Fig. 1). Constant voltage control device for controlling the voltage drop (58 in Fig. 1) on the primary side of the control transformer by controlling According to claim 1 The control transformer (56 in FIG. 1) is a device capable of continuously varying the current (77 in FIG. 1) flowing through the capacitor (74 in FIG. 1) on the secondary side, and a plurality of taps (S1 and S2 in FIG. 1) on the transformer secondary side. , S4, S5) to be contactlessly controlled by the power electronic switch (77 in FIG. 1), and at the same time, a plurality of capacitors (74 in FIG. 1) are installed, and the power electronic switch (75 in FIG. 1) is used. By contact control, the control transformer (56 in FIG. 1) controls the current on the secondary side (77 in FIG. 1) in multiple stages, and controls the voltage drop (58 in FIG. 1) on the primary side of the transformer to control the load stage voltage (FIG. 1). 5) Control device to control constantly According to claim 1 On the secondary side of the control transformer (56 in FIG. 1), a plurality of taps (S1, S2, S4, S5 in FIG. 1) and a plurality of capacitors (74 in FIG. 1) are installed and the power electronic switch (73 and 75 in FIG. 1) is installed. In controlling the current of the transformer 2 side by controlling the current, the control of one of the plurality of capacitors is phase controlled (FIG. 11) to finely control the current (77 in FIG. 1) of the secondary side of the control transformer. Constant voltage controller, The method of claim 1, When a constant power flows into the control transformer by using a control transformer (56 in FIG. 1) that is connected in series with a load (3 in FIG. 1) and used as a voltage drop function, a booster having a secondary voltage higher than the primary voltage is used. The current of the secondary side is made small, so that the current controlled by the power electronic switch (73, 75, 76) is made small, so that the control is easy, the heat generation from the device is small, and the cost is low. 1, 77) constant voltage control device Apparatus for controlling the voltage of the columnar transformer used in the power system by using the constant voltage device having the features of claim 1 Apparatus for controlling the voltage of general household power and industrial power to a constant voltage using the constant voltage device having the features of claim 1 Constant voltage control device having the effect of saving power by constantly lowering the household voltage by using a voltage drop made of low loss by using the constant voltage device having the characteristics of claim 1 Reactive power compensation device using voltage compensator or power factor improvement for capacitor used in secondary side of transformer by using constant voltage device having the features of claim 1