RU2117981C1 - Device for stabilization of transforming station voltage - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: device has converter with direct current circuit and stepping-up transformer which secondary winding is connected to load through converter and which primary winding is connected in series to primary winding of master transformer. Device provides compensation of voltage deviation at output of station without phase shift of load voltage. EFFECT: simplified design, decreased weight and size, improved power characteristics. 2 cl, 2 dwg

Description

 The invention relates to power electronics and can be used to stabilize the voltage on the high side of a step-down transformer substation.

 A device is known for stabilizing the voltage of a transformer substation according to ed. USSR N 1636832, which is taken as a prototype. It contains two booster transformers with primary windings connected in series between input and output terminals, and two inverters connected with their output terminals to the secondary windings of the first and second booster transformers, respectively. Inverters are controlled by a pulse-phase control system as a function of the voltage across the load. The inputs of the inverters are combined and connected through the rectifier to the output terminals of the stabilizer.

 The device can be turned on both on the high and low side of the main transformer of the step-down substation. However, turning it on on the high side complicates the rectifier, inverters and their protection units, but on the low side it does not improve the energy performance of the main transformer of the substation and requires a large cable consumption. In addition, the use of two booster transformers in the device increases the weight and dimensions of the stabilizer and complicates its design.

 The objective of the invention is to simplify the device and improve its overall dimensions and energy indicators without changing the quality of the output voltage.

 As a result of the solution of the task, the power and efficiency factors of the main transformer of the substation are improved, the design is simplified and simplified, because instead of two booster transformers with a 15–20% increase in overall power, one transformer of general industrial design is used. An additional effect of the use of the device during the reconstruction of existing substations should be the reduction in the consumption of active materials of current conductors necessary for installation due to the inclusion of windings of a boost booster transformer in a low current circuit (for a substation of 1000 kV • A with voltages of 6 / 0.4 kV cable consumption, necessary for the installation of the stabilizer is reduced by about 15 times), which can also be attributed to the simplification of the design and the improvement of overall dimensions.

 The technical solution of this problem is achieved by performing a three-phase rectifier with two-way energy exchange and introducing an inductive-capacitive filter, which is connected between the output of the three-phase rectifier and the combined inputs of the inverters, as well as due to the fact that other terminals of the primary winding of the boost transformer are connected to the primary winding of the main transformer, and other terminals of the secondary winding of the boost transformer are connected to the output of the second three-phase inverter.

 Improving the energy performance of the main transformer of the substation by reducing the level of stabilized voltage in the modes close to the idle speed of the substation is achieved due to the fact that a switching device is introduced that changes the value of the reference signal supplied to the comparison element, and a load current sensor 6 is introduced, the output of which is connected to the control input of the switching device (see clause 2).

 The invention is illustrated by the following description and the accompanying drawings, where in FIG. 1 is a block diagram of a device, and FIG. 2 is a diagram of a device with additional elements that change the level of stabilized voltage as a function of the load current.

 The device (Fig. 1) is connected by input terminals to the network 1, and output terminals to load 2 and contains a three-phase main transformer 3 with primary 4 and secondary 5 windings, a three-phase boost transformer 6 with primary 7 and secondary 8 windings, a semiconductor converter 9, which includes two three-phase inverters 10 and 11 with a control system 12, a three-phase rectifier 13 with a control system 14, a filter 15, as well as a voltage sensor 16 and a comparison element 17.

 Elements of the circuit (Fig. 1) are connected as follows.

 The primary winding 4 of the main transformer 3 through the primary winding 7 of the boost transformer 6 is connected to the network 1, and its secondary winding 3 is connected to the load 2, which is also connected to the input of the rectifier 13 and the clock inputs of the control system 14 of the rectifier 13 and the control system 12 of the inverters 10 and 11. The secondary winding 8 of the boost transformer 6 with some of its outputs connected to the output of the first inverter 10, and others to the output of the second inverter 11, the inputs of which are combined and through the filter 15 are connected to the output the rectifier 13. In this case, the control input of the inverter control system 12 is connected to the output of the load voltage sensor 16 through the comparison element 17, and the first and second outputs of the system 12 with the angles of the control pulses α and π-α are respectively connected to the first 10 and second 11 inverters.

 In the embodiment of FIG. 2 modifications of the device with an additional improvement in the energy performance of the main transformer 3, the voltage level at the input of the main transformer 3 is reduced during operation of the substation in the field of deep reduction of loads. This is due to the fact that the load current sensor 18 is introduced complete with measuring current transformers and a switching device 19 (for example, two-stage), the output of which is connected to the subtracting input of the comparison element 17, the control input to the output of the load current sensor 18, and the outputs to signals for setting voltage stabilization levels of the load 2.

 The device (Fig. 1) works as follows.

The first and second three-phase inverters 10 and 11 convert the rectified stabilized voltage U _{2 of} load 2 into phase-variable variable phase voltages with vectors of the first harmonics for one of the phases, respectively
U _f1 = U ₂ e ^jα and U _f2 = U ₂ e ^{j (π-α)} = -U ₂ e ^-jα .
Due to the fact that the inverters 10 and 11 are connected to the secondary winding 8 of the boost transformer 6 on both sides, the voltage difference U _f1 and U _{f2 of the} inverters increased in the transformation coefficient k _w is induced on its primary winding 7
U _d = k _W (U _f1 -U _f2 ) = k _W U ₂ (e ^jα + e ^-jα )
or, taking into account the Euler transforms,
U _d = 2k _W U ₂ cosα.
The voltage U ₁ on the primary winding 4 of the main transformer 3 is determined by the sum of the mains voltage U ₁ and voltage boost U _d
U ₁ = U ₁ + U _d = U ₁ + 2k _vd U ₂ cosα.
The main transformer 3, reducing its input voltage U ₁ k _gt times, generates a load voltage
U ₂ = U ₁ / k _zm = U ₁ / k _zm + 2k _Mo / k _zm U ₂ cosα
or taking into account the voltage deviation ± ΔU ₁ and the voltage drop across the transformers ΔU _to
U ₂ = (U ± ΔU ₁ -ΔU _{to 1)} / (k _zm -2k _W cosα), (1)
where k _gt , k _w are the transformation ratios of the main and boost three-phase transformers;
α is the control angle of the first three-phase inverter.

From the expression (1) it is seen that when the control angle α changes from 0 to π rad. the device (Fig. 1) compensates for both positive and negative deviations of the mains voltage U ₁ , providing stabilization of the output voltage U ₂ at a given, for example, nominal level.

 It should be noted that the voltage boost in the process of stabilizing the load voltage is produced without a shift of the first harmonic, and in the case of an arccine dependence between the angle and the control signal, it is proportional to the voltage deviation in the network.

 The device (Fig. 1) it is advisable to use in powerful electrical installations (about 10 MV • A) with high performance requirements. It, as more perfect, with improved energy and weight and size indicators, can replace the well-known three-phase voltage stabilizers of transformer substations.

Claims (2)

 1. A device for stabilizing the voltage of a transformer substation, which includes a main three-phase transformer with terminals of the secondary winding intended for connecting the load, containing a three-phase boost transformer with primary and secondary windings, a three-phase rectifier with a control system, the input of which is connected to the load, and two three-phase inverters with a common control system for them, the input of which through the comparison element is connected to the output of the load voltage sensor, and the first and second the outputs are connected respectively to the first and second three-phase inverters, providing phase control of the output voltage of the first three-phase inverter by the angle α, and the second by the angle π-α when α changes from 0 to π rad, and the primary winding of the boost transformer is connected to the network with one of its conclusions and its secondary winding is connected with one of its outputs to the output of the first three-phase inverter, characterized in that an inductive-capacitive filter is introduced, which is connected between the output of the three-phase rectifier and the three-phase inverters have three-phase inverters, and the three-phase rectifier is made with two-way energy exchange, the other terminals of the primary winding of the boost transformer are connected to the terminals of the primary winding of the main transformer, and the other terminals of the secondary winding of the boost transformer are connected to the output of the second three-phase inverter.  2. The device according to claim 1, characterized in that a switching device is introduced that changes the value of the reference signal supplied to the comparison element, and a load current sensor is introduced, the output of which is connected to the control input of the switching device.

Images