RU2505918C2 - High-voltage frequency-controlled electric drive - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: in the high-voltage frequency-controlled electric drive, an uncontrolled high frequency converter is connected through a multiple-winding single-phase high-frequency transformer to a controlled high frequency converter having a cellular type, wherein inputs of rectifier-inverter cells are connected to corresponding secondary windings of the single-phase high-frequency multiple-winding transformer, the primary winding of which is connected to the output of the uncontrolled high frequency converter, and the input of the latter is connected through a reactor to the mains supply.

EFFECT: reduced weight and size.

2 cl, 5 dwg

Description

The invention relates to electrical engineering, in particular, to the fields of automated electric drive and converter technology, and is intended to control the speed of asynchronous and synchronous AC motors.

Known are high-voltage frequency-controlled electric drives (hereinafter VFD) for a voltage of 3-10 kV, type ABS ACS5000 (N. Donskoy, A. Ivanov, V. Matison, I. Ushakov "Multilevel autonomous inverters for electric drives and electric power", the journal "Power Electronics ”, 2008, No. 1, Fig. 1 on 44 pages), made on the basis of multi-level inverters and frequency converters (hereinafter referred to as IF). The VFD includes a complex multi-winding transformer operating from an industrial network with a frequency of 50 Hz and adjustable inverter, which can be performed according to various schemes, for example, bridge or cell. With a power of more than 1 MW, the cost of a multi-winding transformer is about 50% of the cost of an electric drive.

The disadvantages of the analogue are increased weight and size and cost indicators of VFD.

High-voltage VFD with a multi-level inverter of the cell type ABS-DRIVE is also known (N.V. Donskoy, A.G. Ivanov, V.A. Matison, I.I. Ushakov "Frequency-controlled high-voltage electric drives" // News of the Academy of Electrotechnical Sciences RF, Moscow, 2010. No. 1, pp. 23-25).

The analogue (see figure 1, which shows a simplified diagram) contains an electric motor 6 and an energy module 1, consisting of interconnected multi-winding transformer 2. with secondary windings 3, an adjustable frequency converter of cell type 4, control system 5. Change in frequency and voltage at the output of the energy module 1, the speed of the electric motor 6. The control system 5 is made on the basis of the controller, and the multi-winding transformer is connected to an industrial network of 6 kV, 50 Hz.

The disadvantage of an analogue is the large size, weight, complexity and high cost of a three-phase transformer 2.

The closest in technical essence to the claimed solution, and taken as a prototype, is an electric motor control device (recommended by FIPS examination in request materials dated 12/07/12) (Utility Model Certificate RU 34295 U 1, H02Р 6/00, 27.11. 2003 )

This device contains a step-up high-frequency transformer connected to an industrial network 380 V, 50 Hz through an unregulated high-frequency converter, the output of the transformer is connected to the electric motor through a rectifier and inverter forming an adjustable frequency converter. In the description of the prototype is a functional diagram of the specified device. By changing the frequency and voltage at the output of an adjustable frequency converter, the speed of the electric motor is regulated. Due to the use of an unregulated high-frequency converter and a step-up high-frequency transformer, the task of reducing the mass and dimensions of the transformer has been solved.

The disadvantages of the prototype:

1. In our opinion, the prototype is practically not operational due to the connection of the high-frequency converter to the network without a reactor (or an equivalent transformer), which should provide: short-circuit current limitation and the derivative of the current through the diodes (when they are switched) of the rectifier installed at the input of the frequency converter, as well as to limit the inrush currents in this rectifier that occur when working with the mandatory capacitive filter at its output (see, for example, G. Zinoviev, Fundamentals power electronics. Publishing house of NSTU, 2003, p.664).

2. In the prototype, a simpler problem is solved - motor control from a frequency converter, consisting of a simple (bipolar in output) rectifier, the output of which is connected to a similar (bipolar in input) inverter. For more complex high-voltage systems, where multilevel adjustable frequency converters are used (as in the analogue), the indicated rectifier and inverter are not suitable. In them, the inverter must also be multi-level, for example, cellular, with a connection to a more complex rectifier unit.

The technical result of the proposed solution is to reduce the overall dimensions of a frequency-controlled electric drive.

The technical result is achieved by the fact that in a high-voltage variable-frequency drive containing respectively connected to each other an electric motor, an unregulated high-frequency converter and an energy module, consisting of a high-frequency transformer and an adjustable frequency converter with a control system, an unregulated high-frequency converter is connected via a multi-winding single-phase high-frequency transformer with adjustable high frequency transformer made by cell of the female type, in which the inputs of the rectifier-inverter cells, consisting of single-phase rectifier blocks with capacitive filters and inverter blocks, are connected to the corresponding secondary windings of a single-phase high-frequency multi-winding transformer, the primary winding of which is connected to the output of the unregulated high-frequency converter, and the input of the latter through the introduced reactor connected to the mains.

In the design of VFD for high power, to the rectifier-inverter cells of each phase of the electric motor are connected, respectively, an unregulated high-frequency converter connected to the corresponding power and connected through the corresponding reactor to the supply network, and a single-phase multi-winding transformer of the energy module.

Due to the implementation of the adjustable frequency converter of the cell type and the connection of the input of the unregulated high-frequency converter to the industrial network through the reactor, as well as the original connection diagram of the component elements of the device, the overall dimensions of the high-voltage VFD are reduced.

Performing a high-frequency adjustable-frequency electric drive with the formation of three blocks for powering each of the three phases of the engine from an individual block of the corresponding power, made on the basis of an unregulated high-frequency converter and an energy module.

The essence of the claimed, alleged invention is illustrated by drawings.

Figure 1 shows a diagram of a prototype,

figure 2 shows a generalized functional diagram of the proposed device,

figure 3 shows a diagram with respect to high-frequency VFD cell type with a single-phase unregulated high-frequency converter and a single-phase high-frequency multi-winding transformer,

figure 4 is a cell diagram of an adjustable frequency converter,

figure 5 shows a diagram of the connection to the VFD of power units (this scheme is suitable for VFD of high power).

The following notation is accepted:

1 - energy module;

2 - multi-winding transformer;

3 - secondary windings of a multi-winding transformer;

4 - adjustable frequency converter;

5 - control system;

6 - AC electric motor;

7 - unregulated high frequency converter;

8 - rectifier block;

9 - filter capacitor;

10 - voltage inverter;

11 -reactor (three-phase or three single-phase);

12 - rectifier-invertor cell;

13 - current sensor;

14 - rectifier block in cell 12;

15 - filter capacitor in cell 12;

16 - inverter block in cell 12, consisting of keys, for example, transistor with reverse diodes;

17 is a power block containing an unregulated high frequency converter 7, for example, at 1000 Hz and the corresponding high-frequency multi-winding transformer 2 of the energy module 1.

Options:

f ₁ - frequency at the output 7, f ₂ - frequency at the output 4;

U is the voltage at the output 4 of FIG. 2 and FIG. 3;

Uy is the control voltage at input 5;

i is a signal from a current sensor 13. The inventive device contains an energy module 1, which includes a transformer 2 with secondary windings 3, an adjustable frequency converter 4, made cell type, control system 5, and an electric motor 6 respectively connected to each other. Multi-winding transformer 2 is single-phase high-frequency, and its primary winding is connected to an unregulated high-frequency converter 7, consisting of a rectifier unit 8, a filter capacitor 9 and a voltage inverter 10, the input of an unregulated high-frequency converter 7 is connected to an industrial network, for example, through a three-phase reactor 11 .

In a cell-type VFD, the secondary windings 3 of a single-phase multi-winding transformer 2 are connected to rectifier-inverter cells 12, connected in series with the corresponding current sensors 13 in the corresponding phases of the electric motor 6. Each cell 12 contains a rectifier block 14, a filter capacitor 15 and an inverter block 16, consisting of keys, for example, transistor with reverse diodes. An unregulated high-frequency converter 7 and a high-frequency multi-winding transformer 2 in a VFD of high power form a power block 17, the number of these blocks is equal to the number of phases of the electric motor 6.

An unregulated high-frequency converter 7 may include a power factor corrector designed to improve electric drive power and with a high-frequency multi-winding transformer 2 can be performed in single-phase or three-phase versions, respectively.

Each rectifier-inverter cell 12 of the adjustable frequency converter 4 is made according to a half-wave rectification scheme. Can be performed with the zero point of the corresponding secondary winding of the multi-winding transformer 2.

The inventive device provides a sharp decrease in the mass and dimensions of the high-frequency multi-winding transformer 2, as well as the number of diodes in the rectifier blocks 14 of the rectifier-inverter cells 12, which improves the overall dimensions and cost of the drive as a whole.

The inventive device operates as follows.

The energy module 1 receives a supply voltage through a multi-winding transformer 2, made high-frequency from an unregulated high-frequency converter 7. This voltage is generated by rectifying the power supply unit at a frequency of 50 Hz by unit 8 and converting it by a voltage inverter 10 to a high frequency, for example, 1000 Hz (voltage inverter 10 is performed, for example, on relatively inexpensive single-operation thyristors).

An unregulated high-frequency converter 7 is connected to the supply network, for example, through a three-phase reactor 11. The power of the three-phase reactor 11 is selected from the condition

,

,

Where

I is the reactor phase current, e _k [%] is the short-circuit voltage reactor, which is comparable with the same value for multi-winding transformer 2, made high-frequency (figure 1) and amounts to about 5%.

It should be noted that for the same values of e _k = 5% and current I (for the transformer and reactor), the power of the transformer

S _TP = 3I · U

20 times higher than the reactor (where U is the phase voltage of the network).

The voltage from the output of the voltage inverter 10 (Fig. 2) is supplied to the high-frequency transformer 2, which distributes it through the secondary windings 3 into the circuit of the adjustable frequency converter 4. The adjustable frequency converter 4 can be performed according to various schemes and generates a variable frequency to control the speed of the electric motor 6, for example, f ₂ = O - 50 Hz and an alternating voltage U from zero to 3 kV or 6 kV. In this case, the speed of the electric motor 6 changes in proportion to the indicated frequency. The control system 5 provides the implementation of the desired control algorithm by simultaneously changing the frequency and voltage, for example, according to the law

.

.

Due to the high frequency f1, the dimensions and consumption of active materials of a multi-winding transformer 2 made by high-frequency, determined by the product of the number of turns W by the cross section of the magnetic circuit Q at a given power, are sharply reduced:

,

,

Where

B _m - maximum working induction in the magnetic circuit.

Multi-winding transformer 2, made high-frequency and voltage inverter 10 can be performed in single-phase or three-phase execution. And the adjustable frequency converter 4 can be performed according to bridge or cell schemes.

Figure 3 shows a diagram of a high-voltage VFD with an adjustable frequency converter 4 cell type. The scheme of the rectifier-inverter cell 12 with a single-phase bridge rectifier block 14 is shown in Fig.4. In order to reduce the number of diodes in the rectifier unit 14 by half and to reduce the power losses in them, this unit in each rectifier-inverter cell can also be performed using a single-phase two-half-period rectification circuit with a zero point corresponding to the secondary winding of a multi-winding transformer. In this case, the voltage inverter circuit in the rectifier-inverter cell and its connection to the filter capacitor and the output of the rectifier block do not change.

The voltage on the electric motor 6 is formed by summing the output voltages of the rectifier-inverter cells 12 according to a given control law. Otherwise, the principle of operation of this circuit is similar to that of FIG. 2. One unregulated high-frequency converter 7 is also used here. However, in high-frequency VFDs, the currents and power of an unregulated high-frequency converter 7 and multi-winding transformer 2 increase. As a result, the practical implementation of an unregulated high-frequency converter 7 and a multi-winding transformer 2 due to the limited power of individual components, for example, the keys of a voltage inverter 10, may not be technically optimal or feasible.

For high-frequency VFD systems (Fig. 5 schematically shows power blocks 17 of high power (for example, an electric drive of more than 5 MW), where instead of one block of an unregulated high-frequency converter 7, three blocks 7 and three high-frequency transformers 2 of lower power are used, forming three power blocks 17 (3 - according to the number of phases ABC of electric motor 6.) Each block 17 provides power to all rectifier-inverter cells 12 of one corresponding phase of the adjustable frequency converter 4. This solution allows optimizing l power multi-winding transformer 2 and unregulated high-frequency converter 7. The control system 5 (figure 2, figure 3) operates in the function of three signals - control, voltage on the motor and current sensors 13.

Thus, due to the implementation of the adjustable high-frequency converter of the cell type, the overall performance of the electric drive is reduced. A multi-winding transformer and an unregulated high-frequency converter form a power unit. For high-frequency VFD systems, several power units are used, and their number is equal to the number of phases of the electric motor. And in each of the power blocks, an unregulated high-frequency converter and a high-frequency multi-winding transformer are made of correspondingly lower power.

Claims (2)

1. A high-voltage frequency-controlled electric drive containing respectively connected to each other an electric motor, an unregulated high-frequency converter and an energy module consisting of a high-frequency transformer and an adjustable frequency converter with a control system, characterized in that the unregulated high-frequency converter through a multi-winding single-phase high-frequency transformer is connected to adjustable high-frequency converter, made cell type, in which the inputs of the rectifier-inverter cells, consisting of single-phase rectifier blocks with capacitive filters and inverter blocks, are connected to the corresponding secondary windings of a single-phase high-frequency multi-winding transformer, the primary winding of which is connected to the output of an unregulated high-frequency converter, and the input of the latter through the input reactor is connected to the mains . 2. The high-voltage frequency-controlled electric drive according to claim 1, characterized in that, in the high-power version, an unregulated high-frequency converter connected to the corresponding power and connected through a corresponding reactor to the supply network and a single-phase multi-winding transformer of the energy module are connected to each phase of the electric motor.

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