RU2297062C2 - Control shutting reactor-autotransformer - Google Patents

Abstract

FIELD: electrical engineering, applicable for compensation of the excessive reactive power of the power line and for the change of the total lever of voltage in it within a wide range.

SUBSTANCE: the device has a magnetic core with yokes and the main rod divided into two longitudinal parts: a rod without air gaps with the control winding and the successive section of the network winding enveloping it positioned around it, and a rod with air gaps. The compensation winding and the general part of the network winding envelop the rod without air gaps with the mentioned windings and the rod with air gaps.

EFFECT: combined functions of control of the reactive power in the reactor-autotransformer and control of the voltage in the power lines within a wide range.

5 cl, 4 dwg

Description

The invention relates to electrical engineering, in particular to controlled shunt reactors-autotransformers (USRAT), 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 simultaneously adjustable inductance of a reactive power compensator, which includes a battery of static capacitors. 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.

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. 1558224, class H01F 29/14 [2]).

Also known is a three-phase controlled autotransformer reactor (URAT), used to improve the operating modes of long-distance power transmission and direct connection to a high-voltage line (USSR Author's Certificate No. 17817111, 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. A change in the ignition angle of the thyristors leads to a decrease (increase) in the indicated current, but higher harmonics are generated in the current of the main winding of URAT. To eliminate odd harmonics, URAT is equipped with phase-shifting and compensation windings, which complicates its design. The main winding of URAT, 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. This magnetic circuit is magnetized by direct current. If there is no magnetization, then the voltage on the DAT winding, connected in series to the main winding, increases, and at a certain level of magnetization it decreases. Thus, the voltage at the middle terminal of the main winding of the URAT, connected, for example, to a power line (power transmission line) can be regulated. However, the voltage varies in the range of (8 ÷ 14)%, which is not enough to carry out deep regulation of the voltage on the line.

A magnetic circuit of a planar design of a single-phase URAT unit can have two rods closed by common yokes. In this case, the phase of the main winding is made of two coils located on different rods and connected so that a circulating magnetic flux is formed in the magnetic circuit of each single-phase unit. Such a design is intended for URAT of greater power [3].

All controlled shunt reactors (CSR) with DC magnetization of the core, including transformer reactors of the type [1], [2], [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 inertia of the reactor associated with the presence of a constant component in the magnetic flux;

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

- insufficient range of voltage regulation on power lines.

The indicated shortcomings of the reactors were largely eliminated in the transformer-type CSR (GN Aleksandrov, High-speed controlled transformer-type reactor 420 kV, 50 Mvar was put into operation. Electricity, 2002, No. 3 [4]). Transformer-type CSR (TT) consists of a five-core solid magnetic circuit and three windings. The control winding (OA) is adjacent to the rod, followed by a compensation winding (KO) and outside the network winding, which is designed for permanent connection to power lines. The op-amp is closed by thyristors by an automatically controlled unit. KO is designed to compensate for higher harmonics and is connected into a triangle.

The short circuit voltage of the CSR TT is approximately 100%, which is ensured by an increase in the winding distance and the number of turns of the windings in comparison with a transformer of the same power. The change in the op amp current by the thyristor blocks leads to the displacement of the magnetic flux from the main rod and, as a result, to an increase in the resistance to this flux, which causes an increase in the reactive current consumed by the CSR CT from the high-voltage power transmission.

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 it and the consumption of reactive power from it with an increase in the active power transmitted through the power lines according to certain laws. 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 combination in USRAT functions of regulation of reactive power and regulation in a wide range of voltage on power lines.

This goal is achieved by the fact that in a controlled shunt reactor-autotransformer containing a magnetic circuit with a main rod, yokes, two side yokes, a network winding located on the main rod, connected by an autotransformer circuit and consisting of a series winding and a common winding with the output of the connection node between them , compensation winding, control winding, controlling the current of the network winding of the unit. Moreover, the main rod is divided into two longitudinal parts: a rod without air gaps and a rod with air gaps, while the rod without air gaps cover the control winding and the serial winding, and the compensation winding and the common winding cover the rod without air gaps with the mentioned windings and the rod with air clearances. The series winding should cover the control winding, and the common winding should be located on top of the compensation winding. The cross section of the rods without air gaps and with air gaps are made in the form of circle segments, with the compensation and common windings placed around the entire circumference, and sequential and control windings around the rod segment without air gaps. Between the ends of all windings and yokes placed ring shunts with a radial cut, and ring shunts are made in a shape corresponding to the cross-sectional shape of the ends of the windings protruding beyond the contours of the magnetic system. The output of the network winding and the output of the connection node between the serial and common windings are connected to the power transmission through switching devices.

The UShRAT design consists of a closed magnetic circuit having a rod without air gaps 1, a rod with air gaps 2, end yokes 3, side yokes 4, upper 5 and lower 6 ring shunts with radial cuts, control windings 7, sequential winding 8, compensation winding 9 , the total winding 10. (Fig.1).

Figure 2 shows a cross section of a single-phase block of a three-phase USRAT. Rods 1 and 2, having a sectional shape in cross section, are covered by the corresponding windings, which are covered by ring shunts from above and below, which pick up the magnetic flux of scattering and direct it to the yokes of the magnetic circuit.

Figure 3 shows a basic single-line circuit of a USRAT, in which a network winding, consisting of a sequential winding 8 and a common winding 10, is included in phase voltage, and a compensation winding 9 connected in a triangle in a three-phase design to suppress the 3rd harmonic, has higher harmonic filters, consisting of a series-connected capacitor 11 and a choke 12, tuned in resonance at the frequency of the suppressed higher harmonics. The control winding 7 is connected to the control unit 13, which is formed on the basis of on-board thyristors and serves to control the current of the network winding.

Figure 4 shows a diagram of the inclusion of USRAT in a super-high voltage main transmission, on which the output of the connection node between the serial and common windings 14 is connected directly to the power line 15 and through the switching device 16 to the buses of the starting (receiving) substation 17. Start of the serial winding 8 connected to the buses 17 also through the switching device 16.

USHRAT is intended to compensate for the capacitive power that is generated by the power transmission line, and to deeply change the voltage on it. The change in the reactive power consumed from the transmission line is carried out by changing the resistance to the main magnetic flux, which closes within the magnetic circuit. With increasing resistance, the magnetizing force (current) of the USRAT network winding increases. Continuous regulation of reactive power consumption is carried out by changing the unlocking angle of the thyristors of the control unit 13. An increase in the current of the control winding 7 causes the magnetic flux to move out of the rod without air gaps 1 and gradually switch it to the rod with air gaps 2. In the short-circuit mode of the control winding 7, carried out by block 13 (the thyristors are fully open), the main magnetic flux is completely displaced from the rod 1 and passes to the rod 2. In this case, the serial winding 8 loses its connection with the main magnetic flux due to its displacement from the rod 1, on which this winding is placed. The short-circuited control winding 7 cannot have flux linkages with a magnetic flux USRAT. Therefore, in the nominal mode (winding 7 is closed), the magnetic flux must be closed in such a way that its total flux linkage with winding 7 is zero while ensuring the required number of flux links with the network winding (windings 8 and 10 are connected in series and according to). This means that the main part of the magnetic flux passes outside the windings 7 and 8 located on the rod 1, through the rod with air gaps 2.

This mode is characterized by the fact that in the serial winding 8 the emf is not induced, directed opposite to the applied voltage. Then the potential of the beginning of the winding 8 is communicated to its end and the voltage applied to the network winding of the USRAT passes to the output of the connection node of the serial and common windings 14, that is, the line is transmitted. LATCH in this mode does not act as a step-down autotransformer (for the starting end of the line), but consumes the maximum reactive power from the line.

где Е₈ и Е₁₀ - э.д.с., индуцируемые основным магнитным потоком соответственно в последовательной 8 и общей 10 обмотках. При вытеснении магнитного потока из стержня без воздушных зазоров 1 происходит снижение э.д.с. E₈ и увеличение коэффициента трансформации К_т и соответственно напряжения на выводе 14 (на линии электропередачи 15).If reactive power consumption from the power transmission line is not required, USRAT works as a normal step-down autotransformer with a transformation ratio

where E ₈ and E ₁₀ - emf induced by the main magnetic flux, respectively, in series 8 and 10 total windings. When the magnetic flux is displaced from the rod without air gaps 1, the emf decreases. E ₈ and an increase in the transformation coefficient K _t and, accordingly, the voltage at terminal 14 (on the power line 15).

To implement the optimal loss mode of the long-distance power line, it is necessary to change the voltage at its end nodes in accordance with the expression

where U _m is the voltage at the beginning (end) of the line, P is the active power at the beginning (end) of the line, g _m is a parameter determined by the generalized constant of the line.

In this case, the reactive power of USRAT at the ends of the line should change in the expression

where Q _m is the reactor power at the beginning (end) of the line, U _m is the optimal voltage value at the beginning (end) of the line, determined by (1), b _m is a parameter depending on the generalized constant of the line (Electrical systems. vol. III Transmission electric energy by direct and alternating current of high voltage. Edited by V.A. Venikov. M: Higher school, 1975 [6]).

The parameters g _m and b _{m are} determined by the formulas

- обобщенные постоянные линии.Where

- generalized constant lines.

The voltage on the line U _m , determined by (1), is proportional to the square root of the active power of the corresponding end of the line. The control current of the control winding 7, carried out by the thyristors of block 13, causes a simultaneous change in the voltage on the line and consumption from the reactive power line. These changes should be as close as possible to the values of U _m , Q _m , determined by (1) and (2), respectively.

It should be noted that increasing the coefficient K _t with increasing current of the control winding 7 leads to a decrease in the equivalent number of turns of the network winding W _c = W ₈ + W ₁₀ , where W ₈ and W ₁₀ is the number of turns of the windings 8 and 10, due to the displacement of the main magnetic flux from the zone of location of the winding 8. With a short-circuited control winding 7, the condition W ₈ ≈ 0 can be accepted and the phase voltage is completely connected to the common winding 10. Therefore, the calculation of the magnetic circuit and the number of turns of the winding 10 should be carried out with this in mind.

A change (increase) in the transformation coefficient K _t , leading to a decrease in the number of turns of the network winding, should be accompanied by an additional increase in the reactive current consumed by USRAT from the power transmission line, based on the ratio

where U _f is the total phase voltage, b _p is the conductivity of the cable. Moreover, the value of b _p increases with increasing K _t in the process of controlling the load mode LATCH. The value of ΔQ should be taken into account when optimizing the power transmission line mode according to the voltage on it and the reactive power consumed by the RED.

The control winding 7 is closed by a thyristor unit 13, designed for the full power of USRAT. With fully open thyristors in the network winding (W _c = W ₈ + W ₁₀ ) and control winding 7, the current is equal to the rated current. This is possible if the short circuit voltage of the USRAT is equal to 100% of its rated voltage. The latter is achieved by the corresponding arrangement of the network and control windings. Most of the network winding - the common winding 10 is located on the magnetic circuit with a large gap relative to the control winding 7 (see figure 1, 2). The serial winding 8, which is an integral part of the network winding, has a smaller gap with the winding 7. However, taking into account the ratio of the number of turns of the windings 8 and 10 W ₈ = (0.25 ÷ 0.3) W _{10 the} value of the short circuit voltage will be determined by the number of turns winding 10 (W ₁₀ > W ₈ }, especially since the action of the winding 8 is excluded with an increase in the reactive current of USRAT.

When the line load is (10 ÷ 20)% of its natural power, P _C USHRAT operates in the autotransformer mode, which reduces the voltage at the beginning of the line by (30 ÷ 35)% of the nominal level. The magnitude of the decrease in the overall level of voltage on the line is consistent with the requirements of maintaining the necessary margin of stability of power transmission.

It should be noted that LOCATION at the starting end of the line works to lower the voltage, and at the receiving end - to increase the voltage to the voltage level of the buses of the receiving node.

In the range of variation of the line load to (0.2 ÷ 0.3) P _{C, the} voltage on the line remains unchanged (for example, U _{power line} = 0.7U _nom . Power _line ). With a further increase in load, the current of the control winding 7 is regulated (increased), due to which the voltage on the line increases and the reactive power consumed from the line increases (according to laws (2) and (3)). This process of simultaneous regulation of voltage and reactive power ends when the voltage on the line is equal to the nominal. For 500 kV lines with a 3-ASO-500 wire brand with a length of 500, 1000, 1500 km, the indicated voltage is achieved with a line load of 0.35 P _C , 0.6 R _C and 1.0 P _C , respectively (for power transmission lines-500 kV R _C = 900 MW).

If voltage regulation on the power transmission line is not required, then USRAT can work in a purely reactor mode. This requires using switching devices 16 to disconnect the serial winding 8 from the buses of the substation 17 and connect the output of the connection node of the windings 8 and 10 (terminal 14) to the buses of the substation 17.

The proposed device USHRAT allows optimal control of ultra-long power lines of ultra-high voltage, which is based on simultaneous deep regulation of the overall voltage level and the consumption of excess power generated by the line. In this case, the change in the transformation coefficient of USRAT is made in a non-contact way by changing the coupling of the main magnetic flux with a serial winding 8.

The use of USRAT in ultra-long power lines allows you to:

- transmission of energy through the line without intermediate reactive power compensation devices;

- successful implementation of power lines with increased natural power due to a more efficient way to compensate for excess line capacitive power;

- lower costs for the construction of power lines;

- more flexible management of normal and post-emergency power transmission modes.

Claims (5)

1. A controlled shunt reactor-autotransformer containing a magnetic circuit with a main rod, yokes, two side yokes, a network winding located on the main rod, connected by an autotransformer circuit and consisting of a series winding and a common winding with a connection node between them, a compensation winding, a winding controls that control the current of the network winding blocks, characterized in that the main rod is divided into two longitudinal parts: a rod without air gaps and a rod with air gaps, wherein the rod without air gaps covers the control winding and the series winding, and the compensation winding and the general winding cover the rod without air gaps with the above windings and the rod with air gaps. 2. The controlled shunt reactor-autotransformer according to claim 1, characterized in that the series winding covers the control winding, and the common winding covers the compensation winding. 3. The controlled shunt reactor-autotransformer according to claim 1 and 2, characterized in that the cross-sections of the rods without air gaps and with air gaps are in the form of circle segments, wherein a compensation winding and a common winding are placed around the entire circumference, and around the rod segment without air gaps serial and control windings. 4. The controlled shunt reactor-autotransformer according to claim 1 and 2, characterized in that between the ends of all windings and yokes there are ring shunts with a radial cut, and the ring shunts are made in a shape corresponding to the cross-sectional shape of the ends of the windings protruding beyond the contours of the magnetic system. 5. The controlled shunt reactor-autotransformer according to claim 1, characterized in that the output of the network winding and the output of the connection node between the serial and common windings are connected to the power transmission via switching devices.

Images