HK1192071A - Power supply arrangement with an inverter for producing n-phase ac current - Google Patents

Description

Power supply device with an inverter for generating an N-phase alternating current

Technical Field

The invention relates to a power supply device comprising an inverter for generating an N-phase alternating current and at least one N-phase alternating current transformer having primary windings and secondary windings, wherein the primary windings are connected in a polygonal manner and the vector sum of the voltages present at the N secondary windings is zero when the transformer is in idle operation.

Background

An unpublished european patent application with application number 11174546.9 discloses a power supply device of this type (see fig. 1 in application 11174546.9). The same application 11174546.9 also discloses that the first power supply device is used for supplying power to silicon rods for the production of polycrystalline silicon according to the siemens process. The first power supply device shown in said application 11174546.9 has three outputs, on which voltages offset by 120 ° with respect to one another are provided. And the intermediate-frequency current with the voltage driving frequency of 1-1000 kHz enters the silicon rod. The voltage is provided by a three-phase alternating current transformer having a primary winding and a secondary winding. The primary windings are delta-connected. The vector sum of the voltages at the three secondary windings is zero when the transformer is in idle operation.

The three secondary windings are connected in series and in parallel with the three outputs of the power supply. The output end is connected with a silicon rod as a load, and the power supply equipment drives current to flow through the silicon rod.

As described in said application 11174546.9, the silicon rod may, in addition to being supplied with electrical power by the first power supply device, be supplied with electrical power by the second power supply device simultaneously with the electrical power being supplied by the first power supply device. And the silicon rods on the second power supply equipment are connected in series. The power supply is realized by a current with a frequency of about 50 Hz.

Application 11174546.9 describes that the second power supply unit is decoupled from the first power supply unit in such a way that the voltage at the output of the first power supply unit connected in series is zero.

In practice, however, problems can arise when the load on the output of the first power supply device is not equally large. In particular, when the self-inductance of one load is greater than the self-inductance of the other load, a considerable difference in the absolute value of the voltage supplied at the output of the first power supply device may partially occur. This results in the sum of said voltages at the output of the first power supply device no longer being 0. Instead, the absolute value may reach several hundred volts. The voltage reached is related to the frequency at which the first power supply device is driven.

The uneven loading of the first power supply device and the resulting voltage at the series output of the first power supply device can lead to damage or destruction of the second power supply device.

Disclosure of Invention

The object of the invention is therefore to further develop the first electrical device in such a way that differences between the absolute values of the voltages at the output of the first electrical device are avoided as far as possible.

This object is achieved according to the invention in that each corner of the polygon formed by the primary winding is connected to an external conductor connection of the inverter via a capacitor.

The capacitors connecting the polygonal corner points and the outer conductor connections can be arranged in the loop circuit of the two loads at the operating time of the power supply system, to ground, i.e. via an intermediate transformer. The capacitor can compensate the absolute difference between the voltages at the output of the power supply unit. The capacitor may have a capacitance of 4 to 6 muF, in particular 4.5 muF. The capacitance at the primary winding end may have a different capacity and a different voltage loading value than the capacitance at the secondary winding end. Typical capacitance values for the secondary winding end capacitance may be 2 muF to 10 muF.

The output of the power supply device is preferably arranged in parallel with the secondary winding.

It is also advantageous if the output of the power supply device is arranged in parallel with a series circuit of a secondary winding and a further capacitor. By means of these further capacitors, the power supply device according to the invention, hereinafter also referred to as first power supply device, can be decoupled from a second power supply device which is connected in parallel with the series circuit at the output of the first power supply device. The further capacitance and the further components together form a high-pass filter which prevents currents driven by the second power supply device and having a lower frequency than the output current of the first power supply device from flowing into the first power supply device and damaging or destroying it.

In the decoupling of the first and second power supply units, too, the voltage at all outputs of the first power supply unit is reduced when the loads are not the same. But not to a significant extent compared to the capacitance at which the outer conductor tab is discarded.

This object is also achieved according to the invention in that the voltage can be adjusted discretely or continuously via at least N-1 secondary windings. Discrete regulation of the voltage can be solved by the secondary winding having a plurality of taps. When the voltage is adjustable through N-1 secondary windings, it can be changed so that the effective value of the voltage over the load connected to the power supply device according to the invention is the same.

Another solution according to the invention is that at least N-1 of the capacitors connected in series with the secondary winding have an adjustable capacitance. It is also achieved by means of such an adjustable capacitance that the effective value of the voltage across the load connected to the power supply device according to the invention is the same.

The inverter may be a bridge circuit having power transistors.

The power supply device may comprise a frequency converter and the inverter may be part of the frequency converter. In addition to the inverter, the frequency converter may comprise a rectifier and a direct voltage intermediate circuit.

Alternatively, the frequency converter may also be a direct converter (direktemrichter). The inverter is then an integrating part of the direct converter according to the invention.

The power supply device according to the invention can be part of a reaction furnace for producing polycrystalline silicon according to the siemens process. The power supply device according to the invention may be a first power supply device for supplying a silicon rod or a silicon slim rod with alternating current for inductively heating. Silicon rods or silicon slim rods may be disposed in the reactor vessel. A support is preset in a reactor container to fix a silicon rod or a silicon slim rod. The support is simultaneously an electrical connector through which the silicon rod or the silicon slim rod is connected with a load circuit.

The reaction furnace may comprise a second power supply device for supplying the silicon rods or silicon slim rods with alternating current for inductively heating. The second power supply device may comprise a transformer with a plurality of secondary winding end taps and a power regulator connected thereto, which operates in voltage sequence control and is connected to the outer conductor connection of the second power supply device output, for example as shown in fig. 1. The frequency of the alternating current that can be generated by the first power supply apparatus is 1 to 1000kHz, and the frequency of the alternating current that can be generated by the second power supply apparatus is 1 to 100 Hz.

Drawings

Further features of the invention are explained below on the basis of preferred embodiments with reference to the drawing. Wherein

Figure 1 shows a circuit diagram of a device consisting of a first power supply device and a second power supply device according to the prior art,

figure 2 shows a circuit diagram of a first power supply device according to the invention,

fig. 3 shows a circuit diagram of a second power supply device according to the invention.

Detailed Description

The device according to the invention shown in fig. 1 comprises a first power supply VSC and a second power supply MF, which are arranged together for supplying electric energy to a load connected to the device. The support is a silicon rod 3 which is located in a reaction furnace for producing polycrystalline silicon by vapor separation according to the siemens process.

In the reactor vessel of the reactor, a holder 7 is provided, which holds the silicon rod 3 on the one hand and establishes electrical continuity between the silicon rod 3 and the reactor electrical connections on the other hand.

The first power supply MF has an input connected to the single-phase ac system external connection L1 and the neutral line N, as does the second power supply VSC. The first power supply device MF comprises an AC-AC frequency converter 1, which is connected to an input of the second power supply device MF.

The AC-AC frequency converter 1 may be a matrix frequency converter by which single-phase alternating current with a frequency of 50 to 60Hz at the input of the AC-AC frequency converter 1 is converted into three-phase alternating current with a frequency of 20 to 200 MHz. The AC-AC frequency converter 1 is thus at the same time a circuit and a frequency converter for converting an input current into a three-phase alternating current. The output of the AC-AC frequency converter 1 is supplied with three-phase alternating current via three outer conductors L1 ', L2 ', L3 '.

The output of the AC-AC frequency converter 1 is connected to a three-phase alternating current transformer 2, whose primary windings 211, 212, 213 are delta-connected. The secondary windings 212, 222, 232 are connected to the connections H ", L1", L2 ", L3" which in pairs form the output of the second power supply device. To these outputs, silicon rods 3 are connected, wherein a first silicon rod 31 is connected to the connections H ", L1", which form a first output, a second silicon rod 32 is connected to the connections L1 ", L2", which form a second output, and a third silicon rod 33 is connected to the connections L2 ", L3", which form a third output of the second power supply MF. Due to the phase angle of 120 ° between the outer conductors, there is no voltage drop across the silicon rods 31, 32, 33 between H "and the connection L3" under symmetrical loading.

The AC-AC frequency converter 1 is controlled by a controller 8, which is not shown in detail here.

Basically, the terminals H "and L3" can be connected without affecting the second power supply apparatus MF. The secondary windings 31, 32, 33 are delta-connected. However, no connection can occur between these two terminals H "and L3", since this also shorts the outer conductor terminal L1 "and the neutral terminal N" of the second voltage supply device VSC. This is not desirable.

Since there is no voltage drop between the connections H "and L3" of the second power supply MF and thus no voltage drop provided by the first power supply MF between the connections L1 "', N"' of the output of the second power supply VSC, the second power supply does not drive a current into the first power supply VSC through the silicon rods 31, 32, 33 when the load is symmetrical.

The second supply unit VSC has inputs which are connected to the outer conductor L1 and the neutral conductor N of the single-phase alternating current system. The second power supply VSC comprises a single-phase alternating current transformer 4, the primary winding 41 of which is connected to the input of the second power supply VSC. The secondary winding 42 of the transformer 4 comprises four taps 421, 422, 423, 424, of which three taps 421, 422, 423 are connected via the power regulators 51, 52, 53 to the outer conductor connection L1' ″ at the output of the second voltage supply VSC. In contrast, the fourth tap 424 is connected to the neutral connection N' ″ of the output of the second voltage supply system VSC.

A fourth tap 424 is preset at the end of the secondary winding 42.

The power regulators 51, 52, 53 are thyristor power regulators, which are formed by two thyristors connected in anti-parallel. The power regulators 51, 52, 53 are driven by voltage sequential control.

The voltage sequence control is effected by a control device 9, which is connected to the thyristors of the power regulators 51, 52, 53 and to other components to be controlled and/or to sensors for detecting current and voltage and to other components not shown.

In order to avoid the second power supply device VSC from reacting on the first power supply device MF, a high-pass filter may be mounted on the output of the first power supply device MF, which is not passed by the output voltage of the first voltage supply device VSC.

The device shown in fig. 1, in particular the first power supply MF, can be expanded in order to be able to connect more silicon rods at more outputs. For this purpose an AC-AC frequency converter with one output for a three-phase alternating current system can be replaced by an AC-AC frequency converter which is provided with outputs for a multi-phase alternating current system with more than three phases, for example for a four-, five-or six-phase alternating current system.

The first power supply device can also be extended by using two three-phase alternating current transformers 2 whose primary windings are connected in parallel in pairs and whose secondary windings are connected in series.

The first power supply device MF provides at its output terminals L1 ", L2", L3 ", H" voltages which are offset by 120 ° from one another and which have the same absolute value in idle operation and in load symmetry at the output terminals L1 ", L2", L3 ", H". The voltage between the terminals L3 ", H" is 0V.

Asymmetrical loads at the connections L1 ", L2", L3 ", H" may result in a different effective voltage at the connections L1 ", L2", L3 ", H". Then the voltage between the connections L3 ", H" is not 0V. Deviations of different orders of magnitude depending on the frequency of the alternating voltage at the output and the type of load may be a problem for connecting the first power supply device MF into a larger device. In particular, in the case of different inductive loads, the ac voltage can deviate during operation of the first power supply device. In particular, when the first power supply device is operated to supply an alternating voltage at a frequency close to the resonant frequency of the output-side circuit, a high voltage may be generated between the connections L3 ", H".

According to the invention, capacitors C11, C12, C13 are connected between the terminals at the output of the AC-AC frequency converter 1 and the corner points of the delta-connected primary windings 211, 212, 213. Fig. 2 and 3 show a first power supply apparatus MF according to the present invention.

The first power supply device MF shown in fig. 2 and 3 corresponds in large part to the power supply device MF shown in fig. 1. Functionally identical parts and assemblies are therefore denoted by the same reference numerals. The second power supply device VSC is not shown in fig. 2. But it can be connected to the loads 31, 32, 33 in the same way as the device shown in fig. 1 and 2.

Fig. 2 and 3 show the AC-AC frequency converter 1 in detail. AC-AC converter 1 refers to a direct current intermediate circuit with rectifier 11, frequency converter 1, with capacitor CG and inverter 12.

The rectifier 11 is connected to the external conductor L1 of the supply network and to the neutral line N. A capacitor CG is connected to the output of the rectifier and forms a dc voltage intermediate circuit. The dc voltage intermediate circuit is connected to the inverter 12.

The inverter 12 is an H-bridge composed of rectifier valves (in particular, IGBTs 121) as it is widely used in inverters. Other controllable switches may be used instead of IGBTs. The points between the rectifier valves 121 of the half bridges of the H-bridge constitute the connections of the output of the inverter 12. The terminals are connected with capacitors C11, C12 and C13. The capacitors C11, C12, C13 are connected to the delta-connected corner points L1 ', L2 ', L3 ' formed by the primary windings 211, 212, 213 of the three-phase alternating current transformer 2. The circuit of the secondary winding of the three-phase alternating current transformer 2 and the loads 31, 32, 33 connected thereto do not differ from the circuit shown in fig. 1.

By means of the capacitors C11, C12, C13, the voltage occurring between the connections L3 ", H" can be significantly reduced when the load is asymmetrical.

The coupling of the output-side current circuit to the primary winding can be produced by the capacitors C11, C12, C13, which leads to a reduction in the voltage across the connections L3 ", H". The voltage on the connections L3 ", H" compensates for the asymmetrical load with respect to the situation described on the basis of fig. 1. The voltage may be reduced by about 100%.

As shown in fig. 3 for the second circuit arrangement according to the invention, when capacitors C21, C22 and C23 are used between the secondary windings 212, 222, 232 of the transformer 2 and the connections L1 ", L2", L3 ", H", a reduction of the voltage between the outer lines of almost 80% is achieved in the case of an ohmic inductive load at the output of the asymmetrical, in particular asymmetrical, first power supply MF, which corresponds to the first circuit arrangement according to the invention according to fig. 2. Although the additional capacitors C21, C22 and C23 prevent a complete symmetry of the output voltage, decoupling of the first power supply MF from the first power supply VSC can be achieved in this way.

Claims (7)

1. Power supply installation (MF) comprising an inverter (12) for generating an N-phase alternating current and at least one N-phase alternating current transformer (2) having primary windings (211, 212, 213) and secondary windings (221, 222, 223), wherein the primary windings (211, 212, 213) are connected in a polygonal shape and the vector sum of the voltages across the N secondary windings (221, 222, 223) is zero when the transformer (2) is in idle operation, characterized in that,

each corner point of the polygon formed by the primary windings (211, 212, 213) is connected to an outer conductor connection of the inverter via a capacitor (C11, C12, C13),

-the voltage can be discretely or continuously regulated by at least N-1 secondary windings (221, 222, 223), and/or

-arranging capacitors in series with the secondary windings (221, 222, 223), wherein at least N-1 capacitors have an adjustable capacitance.

2. A supply device (MF) as claimed in claim 1, characterized in that the output of the supply device (MF) is arranged in parallel with the secondary windings (221, 222, 223).

3. A supply device (MF) as claimed in claim 2, characterized in that the output of the supply device (MF) is arranged in parallel with a series circuit of in each case one secondary winding (221, 222, 223) and in each case one capacitor (C21, C22, C23).

4. Supply device (MF) as claimed in one of claims 1 to 3, characterized in that the inverter (12) is an H-bridge with power transistors (121).

5. A supply device (MF) as claimed in one of claims 1 to 4, characterized in that the supply device comprises a frequency converter (11, 12, CG) and the inverter (12) is part of the frequency converter (11, 12, CG).

6. Reactor for producing polycrystalline silicon according to the siemens process, having a first power supply device (MF) for supplying silicon rods or silicon slim rods which can be arranged in the reactor vessel with alternating current for inductively heating, characterized in that the first power supply device (MF) is a power supply device according to one of claims 1 to 5.

7. The reaction furnace of claim 6, comprising a second power supply apparatus (VSC) for supplying the silicon rods or slim silicon rods with alternating current for inductively heating, wherein the frequency of the alternating current that can be generated by the first power supply apparatus is 10 to 100Hz, and the frequency of the alternating current that can be generated by the second power supply apparatus is 10 to 1000 kHz.