CN103701343B - Three-phase bridge module unit series combination high-voltage transformer - Google Patents

Abstract

The invention provides a high-voltage converter with a series combination of three-phase bridge module units, comprising: 2N three-phase bridge module units and 6 bridge arm inductors, and each three-phase bridge module unit is composed of 6 freewheeling diodes The power switching element and a DC capacitor are formed. The power switching unit of each phase is formed by connecting the positive and negative poles of two power switching elements in series, and the midpoint and the negative pole of the series are the output terminals. The positive poles of the upper power switching elements in the three-phase bridge module unit are connected to each other, and the power switching unit of any one phase is connected in parallel with the DC capacitor. connected to the negative pole. The invention reduces the number of components and modular power units, has simple combination, high reliability and low cost.

Description

Three-phase bridge module unit series combined high voltage converter

technical field

The invention belongs to the field of power electronic converters or high-voltage applications, and relates to the topology structure of a high-voltage converter combined in series with three-phase bridge module units.

Background technique

One of the key technologies to realize high-voltage high-power converters is the high-power converter topology. In recent decades, in-depth research on high-voltage large-capacity converters has been carried out internationally, and many meaningful high-voltage large-capacity topologies have been proposed. The main technologies for constructing topology include: 1. Direct series connection technology of power switching devices. Its advantage is that it can directly apply the existing topology. Consistency requirements are high, and device failures are prone to occur; 2. Multiple technology, its advantage is that the traditional H-bridge or three-phase bridge circuit is coupled through a multi-winding power frequency transformer to achieve high voltage and low harmonic output. The disadvantage is that it needs to use Power frequency multi-winding transformers increase cost, loss, and complexity, and have DC magnetization; 3. Multi-level technology, its advantage is that the DC side uses DC capacitors in series to achieve voltage equalization of power switching devices, and the disadvantage is that the conduction of power switching devices The inconsistency of the current load causes the DC voltage on each DC capacitor to be unbalanced, and the topology is more complicated; 4. The multi-level converter of the module combination is the MMC converter. Its advantage is that each phase bridge arm is composed of multiple identical The modular power unit and the two bridge arm inductors are connected in series to achieve a high degree of modularization. It has more obvious advantages than the general multi-level technology in terms of device current stress, unbalanced operation, and fault protection. It is the current high-voltage electric energy Transform the preferred transformer.

Based on the MMC converter, the present invention proposes a combined high-voltage converter with a higher degree of modularization. The converter proposed by the present invention has the following differences with the MMC converter: 1, the modular power unit is different, the MMC converter adopts a single-phase modular power unit, and the present invention adopts a three-phase bridge-type modular power unit; 2, the combination mode Differently, the MMC converter is a three-phase combination after the modular power units of each phase are combined in series, while the present invention completes the series combination of the three-phase modular power units once. Therefore, compared with the MMC converter, the present invention has the following significant advantages: 1. Reduced components; 2. Reduced the number of modular power units; 3. Simple combination; 4. High reliability; 5. Cost reduction.

Contents of the invention

The present invention proposes a high-voltage converter combined in series with three-phase bridge-type modular units. Compared with the existing high-voltage large-capacity converter, it has a higher degree of modularization, reduces components, reduces the number of power units, and is simple in combination and more reliable. High and low cost, it has broad prospects in high-voltage and large-capacity industrial applications. The present invention is realized through the following technical solutions.

A high-voltage converter combining three-phase bridge module units in series, which includes 2N three-phase bridge module units and 6 bridge arm inductors, wherein the upper bridge arm of the high-voltage converter is connected in series by N three-phase bridge module units Then it is connected in series with one end of three bridge arm inductors, the lower bridge arm is composed of one end of the other three bridge arm inductors and the other N three-phase bridge module units in series, and then the three bridge arm of the high voltage converter The other end of the bridge arm inductance is connected in series with the other end of the other three bridge arm inductances in the lower bridge arm, and there are three bridge arm inductances in the upper bridge arm and three bridge arm inductances in the lower bridge arm. The connection points form the AC output terminals of the corresponding phase bridge arms, and N is a positive integer.

Further, the three-phase bridge module unit is composed of 6 power switching elements with freewheeling diodes and 1 DC capacitor.

Further, in the three-phase bridge module unit, every 2 power switching elements are connected in series to form 1 phase, and 6 power switching elements form 3 phases in total, that is, phase a, phase b and phase c, wherein each phase includes a first switch tube and the second switching tube, the positive pole of the first switching tube is connected to terminal A, and the negative pole is connected to terminal B; the positive pole of the second switching tube is connected to terminal B, and the negative pole is connected to terminal C, where terminal B and terminal C are output terminals , choose phase a, phase b or phase c, the A terminal of the phase A is connected to the positive pole of the DC capacitor, the C terminal is connected to the negative pole of the DC capacitor, and then the A terminals of the three phases a, b, and c are connected, and the voltage on the DC capacitor is E= V/2N, V is the voltage value of the input DC power supply.

Further, the high-voltage converter combined in series with three-phase bridge module units has three working states. The first state is that the second switching tube or the second freewheeling diode of the N three-phase bridge module units on the upper bridge arm is turned on, All other devices are turned off; the second state is that the second switching tubes or second freewheeling diodes of the N three-phase bridge module units of the lower bridge arm are turned on, and all other devices are turned off; the third state is that the upper and lower bridge arms The first switching tubes or the first freewheeling diodes of the 2N three-phase bridge module units are turned on, and all other devices are turned off.

Furthermore, the upper bridge arm of the high-voltage converter is composed of N three-phase bridge module units connected in series with bridge arm inductors in sequence, that is, the B terminals of each phase of the first three-phase bridge module unit are a ₊ , b ₊ , c The ₊ terminal is connected to the positive pole of the power supply, the B terminals of each phase of the first three-phase bridge module unit, namely U _a1 , U _b1 , U _c1 are connected to the positive pole of the power supply, and each phase of the first three-phase bridge module unit The C terminal of the second three-phase bridge module unit is connected to the B terminal U _a2 , U _b2 , U _c2 , according to this connection rule, the B terminal of the i-th three-phase bridge module unit is U _ai , U _bi and U _ci are respectively connected to the C terminals of each phase of the i-1th three-phase bridge module unit, and the C terminals of each phase of the i-th three-phase bridge module unit are respectively connected to the i+1th three-phase bridge module unit The B terminal of the modular unit is U _{a (i+1)} , U _{b (i+1)} and U _{c (i+1)} . After N three-phase bridge module units are connected, the Nth three-phase bridge module unit The C terminal of each phase is respectively connected to the first inductor, the second inductor and the third inductor.

Furthermore, the lower bridge arm of the high-voltage converter is composed of bridge arm inductors connected in series with N three-phase bridge module units in sequence, that is, the fourth inductor, the fifth inductor, and the sixth inductor are connected to the N+1th three-phase bridge module units respectively. The B terminal U _{a (N+1)} , U _{b (N+1)} and U _{c (N+1)} of each phase of the module unit are connected, and the C terminal of each phase of the N+1th module is connected to the N+2th The B terminal of the three-phase bridge module unit is connected with U _{a (N+2)} , U _{b (N+2)} and U _{c (N+2)} . After the three-phase bridge module units are connected, the C-terminals of each phase of the 2Nth three-phase bridge-type module unit, that is, the _a- , b- _, and c _- terminals, are connected to the negative pole of the power supply V.

Compared with the MMC converter, the present invention has the following differences: 1. The modular power unit is different. The MMC converter adopts a single-phase modular power unit, while the present invention adopts a three-phase bridge-type modular power unit; 2. The combination method is different , the MMC converter is a series combination of single-phase modular power units, and then a three-phase combination, while the present invention is completed by a series combination of three-phase modular power units. Therefore, compared with the MMC converter, the present invention has the following significant advantages: 1. Reduced components; 2. Reduced the number of modular power units; 3. Simple combination; 4. High reliability; 5. Cost reduction.

Description of drawings

1a to 1c are structural diagrams of a three-phase bridge module unit of a high voltage converter.

Fig. 2 is the main circuit of the high-voltage converter combined in series with three-phase bridge module units of the present invention.

Fig. 3 is a diagram of three working states of each phase bridge arm in a high-voltage converter combined in series with three-phase bridge module units.

Fig. 4 is a high-voltage converter with series combination of three-phase bridge module units with 2N=4 modules.

Fig. 5 is the output voltage waveform of a three-phase bridge module unit series combined high-voltage converter with 2N=4 modules when 120° control is adopted.

Fig. 6 is the output voltage waveform of a high-voltage converter combined in series with three-phase bridge module units with 2N=4 modules when 180° control is adopted.

specific implementation plan

The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

What Fig. 1 shows is the three-phase bridge type module unit of the present invention, and the composition mode of three-phase bridge type module unit is as follows: comprise 6 power switching elements with freewheeling diode and 1 DC capacitor, every 2 power switching elements are connected in series 1 phase is formed, and they are connected in such a way that the positive pole of the _first switching tube T1 is connected to terminal A, the negative pole is connected to terminal B, the positive pole of the _second switching tube T2 is connected to terminal B, and the negative pole is connected to terminal C, wherein terminal B, The C terminal is the output terminal, and then select a phase or b phase or c phase. The A terminal is connected to the positive pole of the DC capacitor C _E , and the C terminal is connected to the negative pole of the DC capacitor C _E (the voltage _E on the C E=V/2N, V is the voltage value of the input DC power supply), and then connect the A terminals of the three phases a, b, and c.

The high-voltage converter of the series combination of three-phase bridge module units in Figure 2 is constructed as follows: 1. The upper bridge arm is composed of N three-phase bridge module units and bridge arm inductors in series, that is, the first three-phase bridge module unit The B terminals of each phase of M ₁ ie a ₊ , b ₊ , and c ₊ terminals are connected to the positive pole of the power supply V, and the B terminals of each phase of the first three-phase bridge module unit M ₁ are its U _a1 , U _b1 , U _c1 is connected to the positive pole of the power supply V, and the C terminal is connected to U _a2 , U _b2 , and U _c2 of the second three-phase bridge module unit _M2 . According to this rule, the connection mode between the three-phase bridge module units is as follows U _ai , U _bi , and U _ci of the i-th three-phase bridge module unit M _i are respectively connected to the C terminal of each phase of the i-1-th three-phase bridge module unit Mi _-1 , and the i-th three-phase bridge The C terminal of each phase of the modular unit M _i is respectively connected to U _a (i _{+ 1)} , U _{b (i+1)} , U _{c (i+ 1)} , after N three-phase bridge module units are connected, the C terminals of each phase of the Nth three-phase bridge module unit M _N are respectively connected to the first inductance L _ap , the second inductance L _bp and the third inductance L _cp ; 2. The lower bridge arm is composed of bridge arm inductors connected in series with N three-phase bridge module units in sequence. The fourth inductor L _an , the fifth inductor L _bn and the sixth inductor L _cn are respectively connected to the N+1th three-phase bridge The B terminal of each phase of the modular unit M _N+1 is connected with U _{a (N+1)} , U _{b (N+1)} and U _{c (N+1)} , and the N+1th three-phase bridge modular unit The C terminal of each phase of M _N+1 is connected to the U _{a (N+2)} , U _{b (N+2)} , U _{c (N+2)} phases of the N+2th three-phase bridge module unit M _N+2 Connection, according to this rule, after the N three-phase bridge module units are connected, the C terminals of each phase of the 2N three-phase bridge module unit M _2N , that is, the a _- , b _- , c _- terminals are connected to the negative pole of the power supply V; 3. Connect the three-phase bridge arms at the connection points of the upper and lower bridge arm inductances, that is, points a, b, and c. The load can be connected in a three-phase star or delta.

According to the three-phase bridge module unit series combination high-voltage converter topology in Figure 2, each phase bridge arm has three working states, the first state is the upper bridge arm N three-phase bridge module units, that is, M ₁ ~ M _N The second three-phase switching tube T2 or the _second freewheeling diode D2 is turned _on , and other devices are turned off, and the AC output voltage is 2NE=V; the second state is N three-phase bridge modules in the lower bridge arm The unit is the second switching tube T ₂ or the second freewheeling diode D ₂ of the three phases in M _N+1 ~ M _2N is turned on, other devices are turned off, and the voltage of the AC output terminal is 0; the third state is the upper and lower bridges Arm 2N three-phase bridge module units, that is, the first switching tube T ₁ or the first freewheeling diode D ₁ of the three phases in M ₁ ~M _2N is turned on, and other devices are turned off, and the AC output terminal voltage is NE=V /2. Figure 3 shows the corresponding working waveforms of the AC output terminals of each phase.

For the three-phase bridge module unit series combination high-voltage converter shown in Figure 2, there are 2N three-phase bridge module units, and the AC voltage output amplitude is ^2NE (V=2NE) and the three-phase phase difference is 120o through control.

Figure 4 is a high-voltage converter based on the series combination of three-phase bridge module units with 2N=4 modules in Figure 1a, which consists of four three-phase bridge modules M ₁ , M ₂ , M ₃ , M ₄ and 6 bridge The arm inductance is formed, and the inductance values of the six bridge arm inductances are the same, all of which are L. If the 120 ^° conduction method is used for control, the voltages V _a , V _b , V _c of the midpoint of the power supply at points a, b, and c, and the load line voltage V _ab on phase a and phase b are shown in Figure 5; if the 180 ^° conduction method is adopted Control, point a, b, c to power midpoint voltage V _a , V _b , V _c and load line voltage V _ab on phase a and phase b are shown in Figure 6.

Claims (3)

1. a three-phase bridge modular unit tandem compound high tension transformer, it is characterized in that comprising 2N three-phase bridge modular unit and 6 brachium pontis inductance, wherein the upper brachium pontis of high tension transformer is by the most in series with one end of 3 brachium pontis inductance again after the series connection of N number of three-phase bridge modular unit, lower brachium pontis is followed in series to form with other N number of three-phase bridge modular unit by one end of other 3 brachium pontis inductance, then on high tension transformer, the other end of 3 brachium pontis inductance of brachium pontis is connected with the other end of 3 brachium pontis inductance of lower brachium pontis, 3 junction points between 3 brachium pontis inductance and 3 brachium pontis inductance in lower brachium pontis in upper brachium pontis constitute the ac output end of corresponding phase brachium pontis, N is positive integer；Described three-phase bridge modular unit is made up of power switch component and 1 DC capacitor of 6 band fly-wheel diodes；In described three-phase bridge modular unit, every 2 power switch components, 1 phase in series, 6 power switch components constitute 3 phases, i.e. a phase, b phase and c phase altogether, and the most every 1 phase the most each includes the first switching tube (T₁) and second switch pipe (T₂), the first switching tube (T₁) positive pole receive A end, negative pole receives B end；Second switch pipe (T₂) positive pole receive B end, negative pole receives C end, and wherein B end, C end are outfan, selects the A end of a phase or b phase or c phase to receive DC capacitor (C_E) positive pole, C end receive DC capacitor (C_E) negative pole, then the A end of a, b, c three-phase is connected, DC capacitor (C_EThe magnitude of voltage that voltage E=V/2N, V are input DC power on)；Described changer includes 3 kinds of duties, and the first state is the second switch pipe (T of upper brachium pontis N number of three-phase bridge modular unit₂) or the second fly-wheel diode (D₂) conducting, other device is turned off；The second state is the second switch pipe (T of lower brachium pontis N number of three-phase bridge modular unit₂) or the second fly-wheel diode (D₂) conducting, other device is turned off；The third state is the first switching tube (T of 2N three-phase bridge modular unit of upper and lower bridge arm₁) or the first fly-wheel diode (D₁) conducting, other device is turned off.

Three-phase bridge modular unit tandem compound high tension transformer the most according to claim 1, it is characterised in that the upper brachium pontis of high tension transformer is followed in series to form with brachium pontis inductance by N number of three-phase bridge modular unit, first three-phase bridge modular unit (M₁) the B end i.e. a of every phase₊、b₊、c₊End is connected with the positive pole of power supply (V), first three-phase bridge modular unit (M₁) the B end i.e. U of every phase_a1、U_b1、U_c1It is connected with the positive pole of power supply (V), first three-phase bridge modular unit (M₁) the C end of every phase and second three-phase bridge modular unit (M₂) B end i.e. U_a2、U_b2、U_c2It is connected, connects rule, i-th three-phase bridge modular unit (M according to this_i) B end i.e. U_ai、U_bi、U_ciIt is connected respectively to the i-th-1 three-phase bridge modular unit (M_i-1) the C end of every phase, i-th three-phase bridge modular unit (M_i) the C end of every phase is connected respectively to i+1 three-phase bridge modular unit (M_i+1) B end i.e. U_a(i+1)、U_b(i+1)、U_c(i+1), after N number of three-phase bridge modular unit connects, n-th three-phase bridge modular unit (M_N) every phase C end respectively with the first inductance (L_ap), the second inductance (L_bp) and the 3rd inductance (L_cp) connect.

Three-phase bridge modular unit tandem compound high tension transformer the most according to claim 1, it is characterised in that the lower brachium pontis of high tension transformer is followed in series to form with N number of three-phase bridge modular unit by brachium pontis inductance, the i.e. the 4th inductance (L_an), the 5th inductance (L_bn) and the 6th inductance (L_cn) respectively with the N+1 three-phase bridge modular unit (M_N+1) the B end i.e. U of every phase_a(N+1)、U_b(N+1)、U_c(N+1)It is connected, the N+1 module (M_N+1) the C end of every phase and the N+2 three-phase bridge modular unit (M_N+2) the B end i.e. U of every phase_a(N+2)、U_b(N+2)、U_c(N+2)It is connected, according to this rule, after N number of three-phase bridge modular unit of the lower brachium pontis of high tension transformer connects, the 2N three-phase bridge modular unit (M_2N) the C end i.e. a of every phase_-、b_-、c_-End is connected to the negative pole of power supply (V).