RU2360316C2 - Controllable shunting reactor transformer - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: invention is used for compensating excess reactive power of electric power line and for regulating voltage therein within wide ranges in terms of transmitted power. Device consists of magnetic circuit with the main pin where the following is located: power winding consisting of the first and the second in-series connected parts, compensation winding, and control winding earthed to a control unit. By means of the switching devices when setting the above device to compensator transformer mode, the first part of winding is interposed in series of electric power line, and the second part - to the control exciting current unit. All the switching devices and control units are provided on fully controllable semi-conducting power devices, control winding envelopes the main pin, and to compensation winding there connected are upper harmonics filters.

EFFECT: enlarging functional capabilities.

3 cl, 3 dwg

Description

The invention relates to electrical engineering, in particular to controlled shunt reactor transformers (USHRT), and can be used to compensate for the excess reactive power of a high-voltage power line and changes in it over a wide range of the general voltage level.

Known controlled reactor transformer (URT) having a three-phase primary and secondary windings, the latter combined with a DC bias winding (USSR Author's Certificate No. 1541681, class H01F 29/14 [1]).

URT is intended for use at lowering substations of distribution networks as a transformer and at the same time adjustable inductance of a reactive power compensator. At full load of the substation, the URT works as a transformer, if the load is small - in the reactor mode. At an intermediate load, the URT performs the function of both a controlled reactor and a power transformer with an appropriate degree of loading of active and reactive powers. By changing the magnitude of the DC bias, it is possible to adjust the inductive resistance of the primary winding and, as a consequence, the magnitude of the consumed reactive power and the voltage level on the secondary winding.

Similar functions are performed by a three-phase controlled reactor with additional and secondary windings, the first of which is used to magnetize the cores of the magnetic circuit with direct current, and the second is intended to power the load (USSR Author's Certificate No. 1658224, class H01F 29/14 [2]).

Also known is a three-phase controlled autotransformer reactor (URAT), used to improve long-distance power transmission and connected directly to a high-voltage line (USSR Author's Certificate No. 1781711, class H01F 29/14 [3]). The change in reactive power consumed by URAT is carried out by changing the current of the control winding. The magnitude of the current is regulated by in-parallel thyristors connected to its circuit. Changing the opening angle of the thyristors leads to a decrease (increase) in the indicated current, but at the same time higher harmonics are generated in the current of the main winding, for the elimination of which URAT is equipped with compensation windings. The main winding, made by an autotransformer circuit, consists of two parts, between which an additional autotransformer (DAT) of small power is turned on, which has a magnetic circuit separate from URAT, magnetized by direct current. By changing the degree of magnetization, the voltage at the middle terminal of the main winding of the URAT connected to the power line (power transmission line) is regulated. However, the voltage change lies within (8 ÷ 14)%, which is not enough to carry out deep voltage regulation on the line.

All controlled shunt reactors (CSR) with DC magnetization of the core, including transformer reactors of the type [1-3], have serious disadvantages:

- increased content of harmonics in the current of the main winding, caused by saturation of the core and the operation of the thyristors at incomplete opening angles;

- large electrical inertia associated with the presence of a constant component in the magnetic flux;

- a complex control circuit, including additional phase shifting and compensation windings;

- insufficient voltage regulation range, which excludes their use for optimization of long-distance power transmission modes.

A number of shortcomings of the reactors were largely eliminated in transformer-type transformer type (CT) CSR (RF Patent No. 2221297, class H01F 38/02 [4]). CShR TT contains a closed magnetic circuit without gaps, on the main core of which windings are placed: network, control and compensation. The network winding is connected directly to the power transmission line, the control winding is closed to an automatically controlled thyristor unit, and higher harmonics filters are connected to the compensation winding. An increase in the current of the control winding causes the magnetic flux to be displaced from the main rod, which leads to an increase in the resistance to this flux and an increase in the magnetization current (reactive power consumed from the power transmission line).

Managed shunt reactors of all types are designed primarily to maintain voltage in the controlled nodes of high-voltage networks at a given level. At the same time, it is known that in order to optimize the regime of long-distance power lines in terms of active power losses, it is necessary to regulate the overall voltage level on this power line (Venikov V.A., Siuda I.P. Calculations of long-distance AC power transmission modes. Higher School) , 1966 [5]). For optimization, it is necessary to increase the total voltage level on this power line with an increase in the active power transmitted through the power lines according to a certain law. To some extent, such a regime can be provided by the URT and URAT described above. However, due to technical imperfections and an insufficient range of voltage regulation, their use for optimal control of extended power transmission lines is very problematic.

The closest, in technical essence to the proposed device, is URAT according to [3], designed to regulate reactive power and voltage at one of the terminals of the main (network) winding, to which a power line can be connected.

The purpose of the invention is the expansion of the functionality of the device, which allows you to adjust reactive power and in a wide range of voltage on the power lines.

This goal is achieved by the fact that in a controlled shunt reactor-transformer containing a magnetic circuit with a main rod, yokes, two side yokes, a network winding located on the main rod, consisting of two parts having external terminals of the end nodes and connected in series, the first of which is turned on the phase voltage of the power line, the compensation winding, the control winding, the control unit for the current of the network winding, the control unit for the excitation current is inserted into it, the external terminals of the extreme the nodes of the parts of the network winding are connected through switching devices, the first part is connected to the busbars of the terminal substation, the second part is connected to the excitation control unit, which are necessary for switching the device to the operation mode of the boost transformer, in which the first part of the winding is connected to the line cut, the second part to excitation current control unit. The external terminals of the end of the first and beginning of the second parts of the network winding are connected by means of switching devices. All switching devices and controlling the current of the network winding and the excitation current blocks of the device are made on fully controllable power semiconductor devices. The control winding covers the main rod and is closed to the current-controlling unit of the network winding, and the compensation winding is located in the space between the network winding and the control winding, and suppression filters of higher harmonic components are connected to the compensation winding.

The design of the USRT consists of a closed magnetic circuit having a main rod 1, end yokes 2, side yokes 3, upper 4 and lower 5 ring shunts with radial cuts, control windings 6, network winding 7 and compensation winding 8 (Fig. 1).

Figure 2 shows a circuit diagram of a USRT, in which the network winding is divided into the first 9 and second 10 parts connected by the switching device 15. The final outputs of the first part 9 through the switching devices 11 and 12 are connected via a high-voltage switch 19 with buses 20 of the terminal substation . The final outputs of the second part 10 of the network winding through the switching devices 13 and 14 are connected to the output of the drive current control unit 18. The compensation winding 8, connected in a triangle in a three-phase design, is connected to the filters 16 to suppress higher harmonics, consisting of a series-connected capacitor and inductor, tuned into resonance at the frequency of the suppressed higher harmonics (3rd, 5th and 7th). The control winding 6 is connected to the control current of the network winding unit 17, which is formed on the basis of the use of fully controllable semiconductor power devices. On the same devices, a control unit 18 is built, which is designed to change the excitation current of the winding 10 during the operation of the USRT in the mode of a boost booster transformer (VDT), included in the dissection of the power line. In this mode, the winding 10 is the primary (field winding), and the winding 9 is the secondary winding of the RCCB, connected in series to the line.

Figure 3 shows a diagram of the inclusion of CSRT in the long-distance power transmission line of extra-high voltage 22 connected to the buses of the transmitting 20 and receiving 21 of the power systems by means of high-voltage switches 19. The voltage changes (increases) on the power line 22 and remains unchanged on the buses of power systems 20 and 21. USRT the transmitting power system operating in the VDT mode increases the voltage on the line, the control voltage of the receiving power system reduces the line voltage to the voltage level of the buses of this power system.

The process of optimizing the power transmission mode is divided into two stages. With line loads of 30 ÷ 50% of the transmission capacity, automatic voltage regulation is performed at the points of connecting the USRT to the line. To maintain the voltage at a given constant level, the reactive power of CSR Q _* must change in function of the transmitted active power P _* according to the law

where Q _* , P _* are the capacities of the CShRT and the lines, expressed in relative units of the natural power of the line;

λ is the wavelength of the line [5].

Voltage regulation can be carried out by a regulator that affects the change in reactive power of the control switchgear, not as a function of the transmitted power P _* , as follows from law (1), but by the fact that the voltage deviates from the set value. With a positive voltage deviation, the power of the USRT should increase, with a negative deviation, it should decrease. For the stability of the mode, stabilizing signals can be used according to the parameters of the transient process.

In the range of power transmission line changes within 50-100% of its capacity, the voltage on the line is changed according to the law

where Z _C - wave impedance of the line (Ohm);

P is the active power of the line (MW) [5].

If the voltage on the line is regulated according to the law (2), then the transmission mode of natural power will be maintained at any value of power P, which favorably affects the voltage distribution along the line and the level of active power loss.

In the idle mode of the power transmission line and loads not exceeding 50% of the transmission capacity of the power transmission line, the control switchgear in the sending and receiving nodes maintain the voltage at a given level by absorbing excess reactive power that is generated by the line. At the same time, switching devices 11 and 15 are turned on, and 12-14 are turned off. If the load of the lines exceeds the specified value, then the USRT is transferred to the operation mode of the boost booster transformer (VDT). It is assumed that the load of the line is equal to its natural power and the current of the UShRT, which is still operating in the reactor mode, is close to zero. For the transmission line - 500 kV, this power is approximately 900 MW, at which the power generated and consumed by the line is equal and does not require the participation of the control switch in voltage regulation. Under these conditions, the USRT is switched from the reactor mode to the VDT mode.

Initially, the switching apparatus (CA) 15 is turned off, in which the network winding 7 is divided into the first 9 and second 10 parts (the circuit is opened almost at zero current). Then KA12 is turned on, bypassing the turned on KA11, after which KA11 is turned off. Both operations occur when switching currents significantly less than the load current of the line.

It should be noted that before turning on the first part 9 of the network winding, KA13 and KA14 should be included in the line cut, connecting the second part 10 of the network winding with the output terminals of the control unit 18. In this case, in the initial mode, the additional voltage of the control unit 18 applied to the winding 10, should be sufficient to compensate for the voltage drop on the first part 9 of the network winding from the load current of the line.

The device is switched from the VDT mode to the reactor mode when the line load is reduced to the level of natural power with a voltage on it equal to the voltage of the busbars of the terminal substations. In this case, KAI is first turned on and KA12 is turned off, then KA15 is turned on, restoring the complete composition of the network winding 7. The operation of transferring the device to reactor mode is completed by turning off KA13 and KA14.

The operation with the spacecraft for the USRT of the transmitting and receiving nodes is similar despite the fact that the additional voltage produced by the device at these nodes is opposite in sign. In this case, in the transmitting node, additional power is supplied through the device (in the operation mode of the RCCB) to the line, and in the receiving node it is taken from the line by the device and supplied to the secondary voltage buses of this node.

Currently, on the basis of fully controllable power semiconductor devices, contactors (keys) with very high speed and an almost unlimited resource have been developed. At the same time, it becomes possible to switch power circuits in a time not exceeding ten microseconds, i.e. almost instantly (Electrical and electronic devices: Textbook for high schools. / Under the editorship of Yu.K. Rozanov. M., Energoatomizdat, 1998 [6]). To reduce active power losses in the conducting state of semiconductor power devices, hybrid devices based on interconnected thyristors and electromechanical contacts connected in parallel with them can be used [6]. Considering the facilitated working conditions of KA11 and KA12, when the apparatus is turned off (turned on) when the position of another apparatus is switched on (turned off) in parallel, electric automatically controlled apparatuses can be used as working ACs for switching currents significantly less than load currents. KA15 operates in conditions of breaking (connection) of the circuit at idle USRT. Therefore, an electric apparatus with an automatic drive can also be used here.

In the on state, KA13 and KA14 pass current I _B , which is determined by the expression

I _B = ω ₉ / ω ₁₀ · I _L ,

where ω ₉ , ω ₁₀ - the number of turns of the first and second parts of the network winding 7;

I _In - the excitation current of the winding 10;

I _L - line current.

For the implementation of KA13 and KA14, fully controllable power semiconductor devices or hybrid devices based on the parallel connection of power thyristors and electromechanical contacts can be used.

Management of all switching devices is carried out by the regulator of the operating mode UShRT 23 (see figure 2), which also performs the functions of optimal regulation of voltage on the line according to the laws (1) and (2).

Changing the reactive power of the USRT at the first stage of the regulatory process is carried out by changing the resistance to the main magnetic flux, which closes within its magnetic circuit. The increase in the current of the control winding 6, produced by adjusting the control angle of fully controlled semiconductor power devices (thyristors) of the block 17, causes the main magnetic flux to be displaced from the rod 1, on which all the windings are placed, into the gap space between the windings 6 and 7. The latter leads to an increase in the magnetizing current (consumed reactive power) USRT. Reactive power is regulated in accordance with law (1).

To increase the transmission capacity (with an increase in the transmitted power), the overall voltage level of the line is regulated according to the law (2). The controller (23) generates a control action applied to the terminal stage (driver), which generates control signals to turn on (turn off) the fully controlled power semiconductor devices of block 18 in the excitation control circuit (winding 10) of the USRT operating in the VDT mode. The input of block 18 is connected to the secondary voltage buses of the terminal substation, and the output to the winding 10 through the included KA13 and KA14.

The maximum power of the USRT in the VDT mode is determined by the value of the adjustment range for changing the line voltage and the maximum value of its operating current. In the reactor mode, this power is determined by the value of the capacitive power generated by the line at the bus voltage of the end nodes.

The operation of fully controlled power semiconductor devices belonging to block 17 causes higher harmonics in the current of the winding 6. The latter creates the conditions for the appearance of higher harmonics in the magnetic flux of the USRT, which induce higher harmonics in the current of the mains winding 7. Connecting filters of higher harmonic (3rd , 5th, 7th) to the compensation winding 8, located in the space between 6 and 7 windings, provides the proper level of harmonic suppression (Alexandrov G.N. Suppression of higher harmonic in controlled w ntiruyuschih reactors transformer type. Izv. RAN Power 1999, №3 [7]). When connecting the compensation windings of the three phases of the USRT into a triangle, the total power of the filters does not exceed 10% of its power [7].

The operation of the control unit 18, containing fully controllable power semiconductor devices, can cause the appearance of higher harmonics in the magnetic flux of the UShRT and, accordingly, in the current of the secondary winding 9 included in the line cut. The connection of higher harmonic filters (3rd, 5th, 7th) to the compensation winding 8 provides the proper level of harmonic suppression [7].

Block 17, which controls the current of the network winding, and block 18, which controls the field current, are made on the basis of fully controlled artificial semiconductor devices (thyristors). In block 17, phase control of the effective current value is used. The magnitude of the control angle for opening (closing) power semiconductor devices is produced by the regulator 23, which implements the control law (1) or (2), as well as switching devices KA11 - KA15.

The USRT operation in the VDT mode allows increasing the voltage on the line in comparison with the constant voltage on the buses 20 and 21 of the terminal substations. Therefore, at these substations, switchgears and circuit breakers for increased nominal line voltage are not required. USHRT are connected directly to the line (without switches), which is connected to the buses of the terminal substations through switches selected for the rated voltage of the tires (see figure 3). Such a technical solution can significantly reduce the cost of power transmission. A line with a rated voltage of 750 kV can simply be “built-in” into a network with a rated voltage of 500 kV through the use of USRTs that can be tuned to the operating mode of the RCCB with an additional voltage ΔU = 250 kV. In addition, a phased change in transmission capacity is possible. At the first stage, the line operates at a voltage of 500 kV and the USRT at its ends perform the functions of a controlled reactor (regulation law (1)). If it is necessary to increase the transmission capacity of the electric power transmission devices, they are supplemented by an excitation control system with a voltage variation range ΔU = 250 kV. The line with such a phased strategy should be performed in dimensions of 750 kV at a voltage of terminal substations of 500 kV.

The proposed device allows optimal control of ultra-long power lines based on new technology, which provides, depending on the load of the transmission, to conduct a mode with maintaining a constant voltage on the line or changing it in the function of the transmitted power. The latter provides transmission over the natural power line at any load.

Such a control technology when turning on the proposed USHRT at the ends of the line allows:

- energy transmission over an ultra-long line without intermediate reactive power compensation devices and with minimal losses;

- "embed" in the existing system-forming network lines of increased voltage (bandwidth) without the construction of switchgears at substations for this voltage;

- to carry out more flexible control of normal and post-emergency power transmission modes due to high speed and extended regulation range.

Claims (3)

1. A controlled shunt reactor-transformer containing a magnetic circuit with a main rod, yokes, two side yokes located on the main rod, a network winding consisting of two parts having external terminals of the outer nodes and connected in series, the first of which is included in the phase voltage of the line power transmission, compensation winding, control winding connected to the control current of the network winding unit, characterized in that it includes a control unit of the excitation current, external terminals of the extreme nodes The parts of the network winding are connected through switching devices, the first part is connected to the busbars of the terminal substation, the second part is connected to the excitation control unit, which are necessary for switching the device to the boost voltage transformer mode, in which the first part of the winding is connected to the line cut, the second part to the control the excitation current block, while for the separation of the parts of the network winding, the external terminals of the end of the first and the beginning of the second part are connected by means of a switching device, and control of all , Gravitational apparatus produced regulator mode-transformer reactor performing optimum control voltage on the power line. 2. The controlled shunt reactor-transformer according to claim 1, characterized in that all switching devices and controlling the current of the network winding and the excitation current of the device blocks are made on fully controllable power semiconductor devices, and the switching devices of the first part of the network winding are connected to the buses of the terminal substation by high voltage circuit breaker. 3. The controlled shunt reactor-transformer according to claim 1 or 2, characterized in that the control winding covers the main rod, and the compensation winding is located in the space between the network winding and the control winding, and filters for suppressing higher harmonic components are connected to the compensation winding.

Images