RU2576630C2 - Controlled magnetic biased transformer - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention can be used to compensate the reactive power in nodes of a high voltage network and voltage stabilisation, and is intended for the use simultaneously as a transformer, if the voltage from the control device is absent, and a regulated source of the reactive power similarly to the synchronous compensator due to the connection to a secondary winding of the transformer of the capacitor bank, and for the direct current regulation in the control winding. The transformer controlled by magnetic bias differs from the single phase transformers of an armoured type in that at the side rods of the magnetic core additionally control windings are installed, they are connected opposite to the regulated DC source.

EFFECT: invention ensures the possibility of fault due to special manufacturing of the single phase transformer controlled by magnetic bias due to the use of a commercial three phase transformer, in which the side rod windings are used as the control windings.

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Description

The technical field to which the invention relates.

The invention relates to electrical engineering, in particular to controlled sources of reactive power, and can be used to compensate for reactive power in the nodes of the high voltage network and voltage stabilization. UPTr is intended for use simultaneously as a transformer and a regulated source of reactive power.

The level of technology.

Known patent electric reactor with magnetization [1]: [Russia. Patent for invention No. RU 2439730, class. H01F 29/14, 2010]. This reactor consists of two three-phase magnetic cores located in parallel planes. Regulation is realized by magnetizing the phase rods with direct current of the control windings. The disadvantage is the manufacture of a special magnetic circuit with two rods in phase, on each of which are placed the power windings and control windings. Also known patent controlled shunt reactor autotransformer [2]: [Russia. Patent for invention No. RU 2352010, cl. H01F 29/14, C05F 1/10, 2007], in which the regulation of reactive power is realized by connecting the control winding to the thyristor regulator. The disadvantage is the high power of the regulator, equal to the power of the transformer. Proposed in the present invention, the transfer of the control windings to the side rods and the magnetization of the side rods with direct current reduces the power of the controller by more than 100 times, compared with [2].

The purpose of the invention.

Combining the functions of a single-phase armored type transformer and magnetically controlled reactor by placing counter-activated control windings connected to an automatically controlled constant voltage source on the side rods of the armored type transformer. Direct current flowing through the control windings leads to saturation of the side rods of the transformer and to a change in the reactive power consumed by it. In three-phase networks, a group of 3 UPTr is used.

Obtaining an adjustable source of reactive power, similar in function to a synchronous compensator, by connecting a capacitor bank to the secondary winding of the transformer and regulating the direct current in the control winding.

It is possible to refuse the special manufacture of a single-phase UPTr due to the use of a serial three-phase transformer, in which side terminal windings are used as control windings.

Disclosure of the invention.

The design of the UPTr consists of a closed magnetic circuit having a main rod 1, end yokes 2, side rods 3, control windings 4, network (primary) 5 and load (secondary) 6 windings (Fig. 1). A single-phase armored type transformer is used as an UPTr, on the main rod of which there are primary (5) and secondary (6) windings, and on the side rods are two control windings (4).

In FIG. 2 shows a circuit diagram of a winding connection. An external network (electric power system) is connected to the primary winding, and the voltage on this winding is equal to the voltage of the external network. A capacitor bank (KB), a higher harmonic filter (PKU), local load (consumers), and also an auxiliary transformer (supplying a constant voltage source connected to the control windings) can be connected to the secondary winding. The control windings consist of two windings located on the side rods, which are connected in series and counter. Next, the control windings are connected to a capacitor, which shunts the AC component of the voltage of the control winding, and a constant voltage source that performs the function of the control device.

If there is no voltage from the control device (constant voltage source), the controlled transformer works like a normal transformer and its power is equal to the power of the connected loads to the secondary winding. If only a capacitor bank is connected to the secondary winding, then the power of the UPS is equal to the power of the capacitor battery minus losses in the main and load windings.

When a constant voltage source is connected to the control winding, a direct current flows through these control windings, which creates a constant magnetic field and leads to deep saturation of the side rods and a change in the inductance of the network winding. If the capacitor bank in the secondary winding is disconnected, then under the influence of the mains voltage the current of the primary winding increases to the value when the magnetomotive force (ampere) of the primary winding (5) is greater than the magnetomotive force of the current of the control winding (4). The magnitude of the reactive power UPtr is proportional to the magnitude of the current flowing through the control windings, and at rated current in the control windings it is equal to the rated power of the network winding. This property can be interpreted as a change in the inductance of the primary winding under the influence of the current flowing through the control windings.

When a capacitor bank is connected to the secondary winding, the total reactive power is the vector sum of the reactive power of the capacitor bank and the power generated by the control winding.

As a result of the interaction of the control winding with the primary winding through saturated cores, a voltage of 100 Hz is induced in the control winding. Since a capacitor is connected to the control winding, the voltage of 100 Hz on it is small. A current with a frequency of 100 Hz arises in the control winding, the value of which is determined by the resistance of the scattering fields of the control winding. The magnitude of the current frequency of 100 Hz is estimated at 15-20% of the DC component of the control current.

The voltage on the control winding is constant and corresponds to the active resistances of the control windings. The power of the control source in nominal mode is equal to the value of short circuit losses in the control winding. For powerful transformers, the loss is 0.2-0.3% of the winding power. Since two control windings are used, the rated power of the voltage regulator will be equal to 0.4-0.6% of the transformer power. The total losses in the windings at the rated power of the UPtr will be 0.6-0.8% of the power of the UPtr.

The ratio of the cross-sections of the windings UPTr is determined by the planned modes of use. If it is assumed to control the power of the CTF within ± S when the capacitor bank of power S is connected to the winding 2, then the windings 5, 6 have the same cross section, and the winding 4 has a double cross section. If it is planned to switch the capacitor bank depending on the UPr mode, then the windings 4, 5, 6 have the same cross section.

If it is planned to use UPTR only as a controlled source of reactive power, the secondary winding power can be taken equal to 2% of the UPTR power.

To regulate the current flowing through the control windings, an automatic voltage regulator is used in the UPTr connection unit, which allows you to maintain a voltage of a given value due to a change in reactive power. If the three-phase group of UPTr uses one voltage regulator, then it is equivalent to a synchronous compensator (SC). If voltage regulators for each UPTr are used, then the three-phase UPTr group will allow normalizing the voltages of each of their phases and thereby normalizing the voltage of the negative sequence and voltage fluctuations for each phase. If instead of KB, filters of higher harmonics are used, then the three-phase UPTr group will allow normalizing the voltage of higher harmonics in each phase of the connection unit.

As a single-phase UPTr, you can use a serial three-phase transformer. The use of the windings of a three-phase transformer is shown in FIG. 3. The connection of the windings to the network and current regulators is shown in FIG. 4. All transformer windings have the same cross section and the same power. Windings differ in rated voltage. High voltage windings 1, 3, for example 110 kV or 220 kV. 2.4 low-voltage, corresponding to the secondary voltage, for example 10 kV.

To evaluate the power of the control system, the parameters of the serial transformer are used, on the basis of which it is proposed to realize UPTr. For example, if you use a transformer TRDN40000 / 110 with a rated power of St 40 MW with an idle loss of 0.094%, a short circuit of 0.42%, then the power of one phase Sf is 13.3 MW. Active losses in one winding are 0.21% Sph. Based on the active power losses, the rated power of the control current regulator is 0.21% Sf. To accelerate the transient processes in the control winding, a double boost of excitation is used. Accordingly, the voltage of the pathogen increases to a value of 0.4% Uf.

To ensure regulation of the reactive power of the CTF within ± Sf, the capacity of the capacitor bank is Sfn. When the control current is zero, the reactive power is capacitive in nature and is equal to - Sph. Losses in the mains and secondary windings will be 0.42 SF. With a control current equal to the rated one and a disconnected capacitor bank, the reactive power is + Sph. The current regulator can be powered by winding 2. Since the regulator power is less than 1% of the winding power, an increase in winding power is not required.

When voltage regulators are used to control the power of the converter (voltage control in the control winding), the voltage at the measuring point controlled by the voltage regulator will be stabilized.

If you use a three-phase group of 3 transformers, then this group will provide smooth automatic control of reactive power within ± St. According to its capabilities, the combination of UPTr + KB is equivalent to a synchronous compensator. Compared with the SC, in this embodiment, not one, but three three-phase transformers and a capacitor bank are used (the number of transformers triple, but a rotating electric machine is not required and therefore constant maintenance is not required). Cost and losses are almost 2 times less than when using SK, lower operating costs. The small power of the regulators, the ease of maintenance and operation make it justified the widespread use of UPTr in distribution networks to stabilize the voltage, increase reliability due to the rejection of on-load tap-changers on transformers and reduce active power losses.

At present, controlled shunt reactors with magnetization (USHRP), manufactured at the Zaporizhzhya Transformer Plant together with capacitor banks, are used to stabilize the voltage in the nodes of the high voltage network. UPTr solves the same problem, but unlike UShRP, a special product is not required, but serial transformers can be used. The presence of a secondary winding in the UTPr facilitates and reduces the cost of connecting a capacitor bank, since it is connected to a voltage of 10 kV or 35 kV rather than 110 kV and 220 kV, which leads to a significant (5-10 times) reduction in the cost of the circuit breaker and 2- 3 times the entire battery. These properties of UPTr create conditions for improving the operation of distribution networks due to voltage stabilization.

To confirm the properties, UPTr was implemented on a three-phase transformer with a rated voltage of 380 V with a capacity of 820 VA. The phase voltage is 220 V. The nominal phase power is 273 V * A, the current is 1.85 A. The nominal voltage of the secondary winding is 26 V. The transformer was used as a single-phase UTPr with a power of 270 VA. The control characteristics of the UTPr in the mode controlled by magnetization of the reactor are shown in FIG. 5. They show that the reactive power of the CTF is proportional to the control current and the mains voltage. In FIG. Figure 6 shows the waveforms of the current and voltage of the network winding and control winding. The network current is close to sinusoidal. The control voltage is constant and significantly less than the mains voltage. In the control current, in addition to the DC component, there is a current with a frequency of 100 Hz, which improves the shape of the current of the network winding.

The adjusting characteristics of the converter when connecting a capacitor bank are shown in FIG. 7. This figure shows that UPtr can generate and absorb reactive power, that is, operate in synchronous compensator mode.

The dependences of the reactive power of the UPTR on the control currents and on the mains voltage are shown, which show that a change in the control current leads to a change in the input conductivity of the UPTR, which is added to the conductivity created by the capacitor bank.

Claims (1)

A magnetization controlled transformer, which differs from single-phase armored type transformers in that the control side windings are additionally located on the side rods of the core (magnetic core) and are connected in the opposite direction and connected to an adjustable constant voltage source.

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