CN102594160A

CN102594160A - Diode clamped three-level high-voltage matrix converter and modulation method thereof

Info

Publication number: CN102594160A
Application number: CN2012100322082A
Authority: CN
Inventors: 孙尧; 粟梅; 李幸; 王辉; 杨建�; 彭涛; 于晶荣
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2012-02-14
Filing date: 2012-02-14
Publication date: 2012-07-18

Abstract

The invention discloses a diode clamped three-level high-voltage matrix converter and a modulation method thereof. The diode clamped three-level high-voltage matrix converter is a novel high-voltage matrix converter formed by connection of two three-phase bi-directional matrix rectifying modules which are in series connection with one diode clamped three-level inverting module. The matrix converter has the advantages of bidirectional flow of energy, sinusoidal input current, controllable power factors, compact structure, output current of good quality, no requirement for a step of direct current energy storage, strong fault-tolerant capability, and the like, and is particularly suitable for medium high-voltage motor drive and a grid-tied wind power generation system.

Description

Diode clamping type three-level high-voltage matrix converter and modulation method thereof

Technical Field

The invention relates to a diode-clamped three-level high-voltage matrix converter and a modulation method thereof, belongs to the technical field of power electronic equipment, and is suitable for high-voltage and high-power application occasions.

Background

Under the background of the world energy crisis, energy conservation of an alternating current motor speed regulating system utilizing a frequency converter has been listed as a significant measure for implementing the national energy development policy by government competent departments. The traditional PWM frequency converter has the defects that the input end of the traditional PWM frequency converter is a three-phase uncontrollable rectifier bridge, a direct-current energy storage electrolytic capacitor is needed in the middle, the input end power factor is low, the harmonic pollution is serious, the energy can not be fed back, and the like. In recent years, with the rapid popularization of the conventional PWM converter, the negative effects on the peripheral devices are increasingly exposed. Therefore, development of a novel frequency conversion device which is environment-friendly and energy-saving is sought. And the matrix converter is such a green converter. Compared with the traditional PWM frequency converter, the matrix converter omits an intermediate direct-current energy storage link, the power factor is controllable, the input current is sinusoidal (the harm of harmonic waves can be thoroughly eliminated, the line loss in electric energy transmission can be reduced to the maximum extent), the energy can flow in two directions, and when regenerative power generation is carried out, the matrix converter does not need a brake resistor or a special converter, and can directly feed back the electric energy to a power grid, so that the effect of effective energy conservation is achieved.

At present, most of related researches on matrix converters are mainly carried out around the traditional topological structure, and the traditional matrix converter is difficult to be directly suitable for medium-high voltage high-power application occasions due to the physical limitation of devices and the characteristics of the topological structure. However, high-voltage high-power motor systems are widely used in various fields of electric power, metallurgy, petroleum, chemical industry, coal, paper making and the like in China, and in consideration of energy conservation, electric energy quality and production quality, the matrix converter has great demand on high-voltage frequency converter products, has many excellent characteristics as a prominent representative of next-generation frequency conversion products, and cannot be lacked in the field of medium-high voltage application naturally.

For a high-voltage inverter, if a traditional two-level inverter topology structure is adopted, a complex IGBT series connection technology is required, and the following problems exist: high due to high frequency

And surge voltages, which may cause insulation breakdown of the motor rotor winding; secondly, the high-frequency switch generates high device voltage stress and high switching loss, so that the efficiency is reduced; and thirdly, the high-frequency switch generates broadband electromagnetic interference to nearby communication or other electronic equipment. Multilevel inverter technology can overcome the above disadvantages, and thus multilevel structures constitute an effective way to implement high voltage large capacity frequency converters. From the industrial application point of view, there are mainly three types of topologies for multilevel inverters: diode clamping structure, H bridge cascade structure and suspension capacitor structure. Among them, the diode clamping structure and the H-bridge cascade structure are most widely used in the industry. In the field of matrix converters, the matrix converter topology suitable for high-voltage occasions mainly comprises a multi-mode matrix converter invented by J.Change; yong invented capacitive-clamped multilevel matrix converter, but has a large difference from the conventional matrix converter concept due to the energy storage capacitor. The multimode matrix converter is a cascade multilevel matrix converter, which has been successfully applied in the fields of wind power generation and motor speed regulation, and the Japan Anchuan motor company also provides a medium-voltage matrix converter industrial product based on the topological structure. However, the topology needs a large number of power semiconductor devices and a large number of power frequency transformers, the current conversion control is complex, and the fault-tolerant capability is poor. For the above reasons, the present invention proposes a new topology of medium and high voltage matrix converter.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a diode-clamped three-level high-voltage matrix converter and a modulation method thereof, wherein the diode-clamped three-level high-voltage matrix converter and the modulation method thereof have the advantages of continuously adjustable output voltage, excellent input and output electric energy quality performance, no need of an energy storage element, capability of realizing bidirectional energy flow, compact structure, strong fault tolerance, relatively low cost and the like.

The technical solution of the invention is as follows:

a diode clamping type three-level high-voltage matrix converter comprises a three-phase three-winding transformer, a high-voltage rectifier, a three-phase diode clamping type three-level inverter and a controller;

each phase of the three-phase three-winding transformer is provided with a set of primary winding and two sets of identical secondary windings; the high-voltage rectifier is formed by connecting two same three-phase matrix bidirectional rectifier modules in series and forms three output terminals: p, O and N; the three output terminals are respectively connected with the positive pole of a direct current bus, a neutral point and the negative pole of the direct current bus of the three-phase diode clamping type three-level inverter;

three output ends on the alternating current side of the three-phase diode-clamped three-level inverter are output ends of the diode-clamped three-level high-voltage matrix converter;

the high-voltage rectifier and the three-phase diode clamping type three-level inverter are both controlled by the controller.

Each three-phase matrix bidirectional rectifier module is composed of 6 bidirectional switches, each bidirectional switch is formed by reversely connecting two IGBTs in series in a common emitter mode, and each bidirectional switch shares the same trigger pulse.

The three-phase diode-clamped three-level inverter consists of 12 IGBTs with reverse parallel diodes, and each 4 IGBTs are connected in series to form a bridge arm (Q)₁～Q₄、Q′₁～Q′₄、Q″₁～Q″₄) The middle points A, B and C of the upper bridge arm and the lower bridge arm which are respectively 2 and three bridge arms are used as the output ends of the inverter module, and each bridge arm is provided with 2 clamping diodes (D)₁～D₂、D′₁～D′₂、D″₁～D″₂) Two by two are connected in series to form a branch bridge arm, the upper end of the branch bridge arm is connected with an upper main bridge arm switch (Q)₁ Q₂、Q′₁ Q′₂、Q″₁ Q″₂) Between, the lower end is connected with a lower main bridge arm switch (Q)₃ Q₄、Q′₃ Q′₄、Q″₃ Q″₄) In the meantime.

The primary winding side of the three-phase three-winding transformer is connected with a filter reactance and a damping resistor, and the secondary winding side of the three-phase three-winding transformer is connected with a filter capacitor.

A modulation method based on the diode-clamped three-level high-voltage matrix converter is characterized in that the duty ratio of a rectification stage is

m is the modulation coefficient of rectifier stage, m is more than 0 and less than or equal to 1, d_i1，d_i2For duty ratio, θ is reference current vector angle, n is sector number of reference current vector in sector I, n is 1, d_i1Is a two-way switch S₁，S′₁，S₅And S'₅On duty ratio, d_i2Is a two-way switch S₁，S′₁，S₆And S'₆A duty cycle of on; if the reference current vector is in sector II, n is 2, d_i1Is a two-way switch S₁，S′₁，S₆And S'₆On duty ratio, d_i2Is a two-way switch S₂，S′₂，S₆And S'₆A duty cycle of on; if the reference current vector is in sector III, n is 3, d_i1Is a two-way switch S₂，S′₂，S₆And S'₆On duty ratio, d_i2Is a two-way switch S₂，S′₂，S₄And S'₄A duty cycle of on; if the reference current vector is in sector IV, n is 4, d_i1Is a bidirectional switch S2, S'₂，S₄And S'₄On duty ratio, d_i2Is a two-way switchS₃，S′₃，S₄And S'₄A duty cycle of on; if the reference current vector is in sector V, n is 5, d_i1Is a two-way switch S₃，S′₃，S₄And S'₄On duty ratio, d_i2Is a two-way switch S₃，S′₃，S₅And S'₅A duty cycle of on; if the reference current vector is in sector VI, n is 6, d_i1Is a two-way switch S₃，S′₃，S₅And S'₅On duty ratio, d_i2Is a two-way switch S₁，S′₁，S₅And S'₅The on duty cycle.

Duty cycle of rectifier stage is

Wherein

When the reference current vector is located in sector I, d_αIs a two-way switch S₁，S′₁，S₅And S'₅Duty ratio when all other switches of the rectifier are turned off, corresponding DC voltage u_dc＝2u_ab(ii) a And d_βIs a two-way switch S₁，S′₁，S₆And S'₆On, the duty ratio of all other switches of the rectifier is in the off state, and the corresponding direct current voltage is u_dc＝2u_acThe mean DC average voltage is u_dc＝2(u_abd_α+u_acd_β)；

When the reference current vector is located in sector II, the DC voltage u_dc＝2(u_acd_α+u_bcd_β) (ii) a When the reference current vector is located in sector III, the DC voltage u_dc＝2(u_bcd_α+u_bad_β) (ii) a When the reference current vector is located in sector IV, the DC voltage u_dc＝2(u_bad_α+u_cad_β) (ii) a When the reference current vector is located in the sector V, the DC voltage u_dc＝2(u_cad_α+u_cbd_β) (ii) a When the reference current vector is located in sector VI, the direct current u_dc＝2(u_cbd_α+u_abd_β)。

The modulation signals of the inverter (i.e. the three-phase diode-clamped three-level inverter) are as follows:

<math> <mrow> <msub> <mover> <mi>u</mi> <mo>&OverBar;</mo> </mover> <mi>io</mi> </msub> <mo>=</mo> <mn>2</mn> <mfrac> <msub> <mi>u</mi> <mi>io</mi> </msub> <msub> <mi>u</mi> <mi>dc</mi> </msub> </mfrac> <mo>,</mo> <mi>i</mi> <mo>&Element;</mo> <mo>{</mo> <mi>A</mi> <mo>,</mo> <mi>B</mi> <mo>,</mo> <mi>C</mi> <mo>}</mo> <mo>;</mo> </mrow> </math>

wherein the inverter modulation signal before normalization is

\{\begin{matrix} u_{Ao} = u_{A}^{*} + u_{no} \\ u_{Bo} = u_{B}^{*} + u_{no} \\ u_{Co} = u_{C}^{*} + u_{no} \end{matrix},

Wherein,

u_{no} = - \frac{\min {u_{A}^{*}, u_{B}^{*}, u_{C}^{*}} + \max {u_{A}^{*}, u_{B}^{*}, u_{C}^{*}}}{2}

is a zero-sequence signal and is used as a zero-sequence signal,

is the desired output voltage.

Has the advantages that:

the diode-clamped three-level high-voltage matrix converter adopts a novel high-voltage matrix converter formed by connecting two three-phase bidirectional matrix rectifying modules connected in series with a single diode-clamped three-level inverter module. The matrix converter has the excellent characteristics of bidirectional energy flow, sinusoidal input current, controllable power factor, compact structure, high-quality output current, no need of a direct-current energy storage link, strong fault-tolerant capability and the like, and is particularly suitable for medium-high voltage motor driving and grid-connected wind power generation systems.

The rectifying stage of the high-voltage matrix converter provided by the invention adopts the bidirectional switch, so that energy can flow in two directions. Because an intermediate energy storage link is not needed, the structure is compact, and the power volume ratio and the power weight ratio are high. Meanwhile, due to the multi-level characteristic, the harmonic distortion rate of the output current is smaller, and the switching frequency is allowed to be lower, so that the switching frequency converter is particularly suitable for high-voltage high-power application. The topology is capable of fault tolerant operation even when an open circuit fault occurs in a rectifier module, such as one or more switches of the upper half of the rectifier module of the high voltage rectifier 4 (if S occurs₁) When an open-circuit fault occurs and is detected in time, all switches of the rectifier module in the upper half part and Q of the inverter part are closed₁，Q′₁And Q ″)₁The two-level inverter is formed to continuously operate, so that the two-level inverter has certain fault-tolerant capability. The rectifier-stage bidirectional switch of the high-voltage matrix converter with the structure allowsZero current commutation is allowed, so that the control is simple, the switching loss is small, and the system efficiency is high. Based on the characteristics, the diode-clamped three-level high-voltage matrix converter is a novel high-voltage frequency converter with excellent performance.

Drawings

Fig. 1 shows a diode-clamped three-level high-voltage matrix converter topology.

Fig. 2 shows the intermediate dc voltage of a three-level matrix converter.

Fig. 3 is a view of the input current vector of fig. 3.

Fig. 4 is a schematic diagram of the rectifier switching signal (sector I).

Fig. 5 is a schematic diagram of multi-carrier modulation at the inverting terminal of the three-level matrix converter.

Fig. 6 is a control block diagram of a three-level high voltage matrix converter system.

Fig. 7 shows input voltage (phase voltage) and input current waveforms.

Fig. 8 is an output current waveform.

Fig. 9 is an output line voltage waveform.

Detailed Description

The invention will be described in further detail below with reference to the following figures and specific examples:

a diode-clamped three-level high voltage matrix converter as shown in figure 1 is composed of an input filter (including a filter reactance and a damping resistor)1Filter capacitor2) Three-phase three-winding transformer3High-voltage rectifier formed by connecting two same three-phase bidirectional matrix rectifier modules in series4And a conventional three-phase diode clamping type three-level inverter5And (4) forming.

The input filter is a second-order LC low-pass filter, and it should be noted that the filter capacitor should be arranged in the three-phase three-winding isolation transformer3As far as possible with a high-voltage rectifier4The ac input side is close to relieve the transformer leakage inductance and the like from stressing the matrix converter semiconductor devices. The LC filter filters out higher harmonics from the matrix converter on one hand to enable the input current to reach the standard of the power quality requirement of the power grid, and on the other hand, can prevent the influence of voltage harmonics and the like from the power grid on the output current of the matrix converter to a certain extent. Wherein, only one set of filter reactance is needed, and the filter capacitor2Two sets are required. High-voltage rectifier4Two sets of three-phase bidirectional matrix rectifier modules are connected in series in the manner shown in figure 1, and the high-voltage rectifier4Has three terminals: p, O and N. When the control signals of the two sets of three-phase bidirectional matrix rectifier modules are completely the same, U exists_PO＝U_ON. The high-voltage rectifier is composed of a bidirectional switch, so that power can flow in two directions, and the two matrix rectifier modules are connected in series, so that the rectification voltage multiplication can be realized in a safe voltage range which can be borne by a switching device, higher available direct-current voltage can be provided for an inversion end, and high-voltage inversion is realized. High-voltage rectifier4P, O and N at output end are respectively clamped with a conventional three-phase diode three-level inverter5The positive pole of the direct current bus, the neutral point and the negative pole of the direct current bus are connected. Three-level inverter with output voltage clamped by diode5Unlike conventional applications, in which the dc bus voltage is a time-varying dc voltage as shown in fig. 2, common modulation strategies such as carrier modulation and control vector modulation concepts are still applicable here, but the adverse effect of the time-varying dc voltage on the resultant output voltage needs to be eliminated by modifying the modulation signal. The above is related to the topology of the diode-clamped three-level high-voltage matrix converter, and the following is the modulation strategy related thereto.

The modulation strategy consists of two components: a rectifier-level modulation strategy and an inverter modulation strategy.

Assuming an input voltage:

referring to FIG. 3, the duty cycle of the rectifier stage has

Where m is the modulation factor of the rectifier stage, d_i1，d_i2For duty cycle, θ is the reference current vector angle, n is the sector number of the reference current vector, e.g. if the reference current vector in fig. 3 is in sector I, n is 1, d_i1Is a two-way switch S₁，S′₁，S₅And S'₅On duty ratio, d_i2Is a two-way switch S₁，S′₁，S₆And S'₆The on duty cycle. If the reference current vector is in sector II, n is 2, d_i1Is a two-way switch S₁，S′₁，S₆And S'₆On duty ratio, d_i2Is a two-way switch S₂，S′₂，S₆And S'₆The on duty cycle. If the reference current vector is in sector III, n is 3, d_i1Is a two-way switch S₂，S′₂，S₆And S'₆On duty ratio, d_i2Is a two-way switch S₂，S′₂，S₄And S'₄The on duty cycle. If the reference current vector is in sector IV, n is 4, d_i1Is a two-way switch S₂，S′₂，S₄And S'₄On duty ratio, d_i2Is a two-way switch S₃，S′₃，S₄And S'₄The on duty cycle. If the reference current vector is in sector V, n is 5, d_i1Is a two-way switch S₃，S′₃，S₄And S'₄On duty ratio, d_i2Is a two-way switch S₃，S′₃，S₅And S'₅The on duty cycle. If the reference current vector is in sector VI, n is 6, d_i1Is a two-way switch S₃，S′₃，S₅And S'₅On duty ratio, d_i2Is a two-way switch S₁，S′₁，S₅And S'₅The on duty cycle.

In order to maximize the direct current utilization rate, the duty ratio is normalized

According to fig. 3, d is when the reference current vector is located in sector I_αIs a two-way switch S₁，S′₁，S₅And S'₅On, the duty ratio of the rectifier when all other switches are closed, and the corresponding direct current voltage u_dc＝2u_ab(ii) a And d_βIs a two-way switch S₁，S′₁，S₆And S'₆On, the duty ratio of all other switches of the rectifier is in the off state, and the corresponding direct current voltage is u_dc＝2u_acThe corresponding switching signal is shown in fig. 4, so the intermediate dc average voltage can be expressed as

u_dc＝2(u_abd_α+u_acd_β) (4)

If the reference current vector is located in sector II, the DC voltage u_dc＝2(u_acd_α+u_bcd_β) (ii) a When the reference current vector is located in sector III, the DC voltage u_dc＝2(u_bcd_α+u_bad_β) (ii) a When the reference current vector is located in sector IV, the DC voltage u_dc＝2(u_bad_α+u_cad_β) (ii) a When the reference current vector is located in the sector V, the DC voltage u_dc＝2(u_cad_α+u_cbd_β) (ii) a When the reference current vector is located in sector VI, the direct current u_dc＝2(u_cbd_α+u_abd_β)。

Setting a desired output voltage

The invention adopts carrier modulation to realize the inversion modulation of the high-voltage matrix converter, and generally, the implementation of the carrier modulation needs to select proper modulation waves and carriers. First, the inverter modulates the signal to be

\{\begin{matrix} u_{Ao} = u_{A}^{*} + u_{no} \\ u_{Bo} = u_{B}^{*} + u_{no} \\ u_{Co} = u_{C}^{*} + u_{no} \end{matrix} - - - (6)

Wherein, the zero sequence signal satisfies:

for the sake of simplicity, the invention takes

u_{no} = - \frac{\min {u_{A}^{*}, u_{B}^{*}, u_{C}^{*}} + \max {u_{A}^{*}, u_{B}^{*}, u_{C}^{*}}}{2} - - - (7)

For the sake of processing simplicity, the modulation signal is subjected to normalization processing as shown in (8):

<math> <mrow> <msub> <mover> <mi>u</mi> <mo>&OverBar;</mo> </mover> <mi>io</mi> </msub> <mo>=</mo> <mn>2</mn> <mfrac> <msub> <mi>u</mi> <mi>io</mi> </msub> <msub> <mi>u</mi> <mi>dc</mi> </msub> </mfrac> <mo>,</mo> <mi>i</mi> <mo>&Element;</mo> <mo>{</mo> <mi>A</mi> <mo>,</mo> <mi>B</mi> <mo>,</mo> <mi>C</mi> <mo>}</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>8</mn> <mo>)</mo> </mrow> </mrow> </math>

the inversion modulation of the matrix converter is different from the modulation strategy of a conventional diode-clamped three-level inverter, because the intermediate direct-current voltage of the matrix converter is synthesized by two line voltages of a power supply according to a certain combination mode, each complete inversion modulation period of the matrix converter is formed by two sub-inversion processes together, fig. 5 is a typical inversion process, and if the reference current vector of the matrix converter is located in a sector I, the front-stage direct-current voltage is 2u_abCarrier period of d_αT_s(ii) a The rear-end DC voltage is 2u_acCarrier period of d_βT_sAccording to (3), we know that d_α，d_βIs a function of the vector angle of the reference current, so that the carrier period is time-varying, while the intermediate dc voltage u is readily found_dcAlso a time variable.

As can be seen from fig. 5, the key to implementing the inverse modulation of the matrix converter is the calculation of the modulation signal and the generation of the variable-period carrier signal, wherein the modulation signal is calculated by equation (8); the period information of the variable period carrier signal is provided by equation (3), d_αT_sAnd d_βT_sWherein T is_sThe system modulation period. The invention adopts the positive and negative opposite stacking type multi-carrier modulation technology, so the invention has the advantages of sharingTwo carrier generators for generating two paths of isosceles triangle carrier signals with varying periods and 180 deg. phase difference, the waveforms of which are shown in fig. 5. They may be implemented by counters and comparators etc. in a CPLD or Field Programmable Gate Array (FPGA).

Example 1:

the topology and control concept of the present invention is illustrated with reference to fig. 6. In fig. 6, the main circuit comprises a filter reactance and a damping resistor1Filter capacitor2Three-phase three-winding transformer3High voltage rectifier4Three-phase diode clamping type three-level inverter5And a driving circuit8Six parts, the control circuit is composed of a sampling circuit6And a controller7And (4) forming. Filter reactance and damping resistance1The left ends a, b and c of the three-phase transformer are respectively connected with the three phases of a three-phase power grid, and the right ends of the three-phase transformer are connected with a three-phase three-winding transformer3The primary windings of the coils are connected. Three-phase three-winding transformer3Two sets of secondary windings and filter capacitors2Connected in parallel and then respectively connected with a high-voltage rectifier4The alternating current input sides of the two sets of three-phase matrix rectifiers are connected, wherein the two sets of secondary windings are completely the same in configuration. High-voltage rectifier4Three output terminals: p, O and N are respectively clamped with three-phase diode type three-level inverter5The positive pole of the direct current bus, the neutral point and the negative pole of the direct current bus are connected. Three-phase diode clamping type three-level inverter5The output terminals A, B, C of the transformer can be connected with various inductive loads. Wherein, the high-voltage rectifier4Comprising 12 bidirectional switches9Make up of, and switch in two directions9The two common emitter IGBTs are connected in series in an inverted manner and share the same driving signal. Three-phase diode clamping type three-level inverter5The power converter consists of 12 IGBTs with reverse parallel diodes, and 4 IGBTs are connected in series to form a bridge arm Q₁～Q₄、Q′₁～Q′₄And Q ″)₁～Q″₄The upper part and the lower part of each bridge arm are respectively 2, and the middle points of the three bridge arms are used as the output ends of the inversion modules. On each arm, there are 2 clamping diodes (D respectively)₁～D₂、D′₁～D′₂And D ″)₁～D″₂Correspond toBranch bridge arms of ABC phases) are connected in series to form branch bridge arms and are connected in parallel with two IGBTs in the middle of the main bridge arm, namely the upper ends of 3 branch bridge arms are respectively connected with an upper main bridge arm switch Q₁ Q₂、Q′₁ Q′₂And Q ″)₁ Q″₂Between the two main bridge arm switches Q and at the lower end of the two main bridge arm switches Q₃ Q₄、Q′₃ Q′₄And Q ″)₃ Q″₄In the meantime.

Sampling circuit6Responsible for three-phase three-winding transformer2Secondary square voltage u_a，u_b，u_cSignal conditioning and control device7The DSP is responsible for sampling, calculating and other works, when the calculation is finished, the required information is transmitted to the CPLD, and finally the CPLD completes all modulation tasks and transmits each switch signal to the drive circuit8Thereby achieving the purpose of controlling each switch.

In terms of algorithm, the implementation steps are as follows: first, collecting voltage u_a，u_b，u_cAnd calculating an input current reference vector according to the requirement of the power factor. And secondly, selecting a rectifier switch combination according to a sector where the input current reference vector is located, calculating the duty ratio of each switch combination according to the formulas (2) and (3), and calculating the middle average direct current voltage to prepare for subsequent inversion modulation. And thirdly, reading the expected output voltage, and solving a normalized modulation signal according to the (6), (7) and (8). And fourthly, generating driving signals of all switches of the high-voltage matrix converter by the CPLD according to the information obtained by calculation in the steps.

Case description:

the input power grid voltage is 3300V, the transformer primary-secondary transformation ratio is 1: 1, the output reference voltage is 5500V/30Hz, the output load is a series inductance-resistance load, R is 20 omega, L is 50mH, and the input filter parameters are: l is_s＝0.6mH，R_s＝3Ω，C_f30 muf, the sampling frequency and switching frequency is 10 KHz.

In thatMATLAB/Simulink environmentLower pairThe system was simulated and fig. 7 shows the input voltage (phase voltage) and input current waveforms, the input current being sinusoidal and having a basic unity power factor. Fig. 8 shows an output current waveform, which has a good quality due to the multi-level characteristic. Fig. 9 is an output line voltage waveform, and it is apparent that the output line voltage has a multi-level characteristic.

Claims

1. A diode clamping type three-level high-voltage matrix converter is characterized by comprising a three-phase three-winding transformer, a high-voltage rectifier, a three-phase diode clamping type three-level inverter and a controller;

2. The diode-clamped three-level high-voltage matrix converter according to claim 1, wherein each three-phase matrix-type bidirectional rectifier module is composed of 6 bidirectional switches, each bidirectional switch is composed of two IGBTs with common emitters connected in reverse series, and each bidirectional switch shares the same trigger pulse.

3. A diode-clamped three-level high-voltage matrix converter according to claim 2,

4. A diode-clamped three-level high voltage matrix converter according to any of claims 1-3, wherein the primary winding of the three-phase three-winding transformer is flanked by a filter reactance and a damping resistance, and the secondary winding of the three-phase three-winding transformer is flanked by a filter capacitance.

5. A method of modulating a diode-clamped three-level high-voltage matrix converter according to claim 3, characterized in that the duty cycle of the rectifier stage is

m is the modulation coefficient of rectifier stage, m is more than 0 and less than or equal to 1, d_i1，d_i2For duty ratio, θ is reference current vector angle, n is sector number of reference current vector in sector I, n is 1, d_i1Is a two-way switch S₁，S′₁，S₅And S'₅On duty ratio, d_i2Is a two-way switch S₁，S′₁，S₆And S'₆A duty cycle of on; if the reference current vector is in sector II, n is 2, d_i1Is a two-way switch S₁，S′₁，S₆And S'₆On duty ratio, d_i2Is a two-way switch S₂，S′₂，S₆And S'₆A duty cycle of on; if the reference current vector is in sector III, n is 3, d_i1Is a two-way switch S₂，S′₂，S₆And S'₆On duty ratio, d_i2Is a two-way switch S₂，S′₂，S₄And S'₄A duty cycle of on; if the reference current vector is in sector IV, n is 4, d_i1Is a two-way switch S₂，S′₂，S₄And S'₄On duty ratio, d_i2Is a two-way switch S₃，S′₃，S₄And S'₄A duty cycle of on; if the reference current vector is in sector V, n is 5, d_i1Is a two-way switch S₂，S′₃，S₄And S'₄On duty ratio, d_i2Is a two-way switch S₃，S′₃，S₅And S'₅A duty cycle of on; if the reference current vector is in sector VI, n is 6, d_i1Is a two-way switch S₃，S′₃，S₅And S'₅On duty ratio, d_i2Is a two-way switch S₁，S′₁，S₅And S'₅The on duty cycle.

6. The modulation method of a diode clamped three level high voltage matrix converter according to claim 5 wherein the rectification stage duty cycle is

Wherein

When the reference current vector is located in sector I, d_αIs a two-way switch S₁，S′₁，S₅And S'₅Duty cycle of conduction, when all other switches of the rectifier are closedCorresponding direct voltage u_dc＝2u_ab(ii) a And d_βIs a two-way switch S₁，S′₁，S₆And S'₆On, the duty ratio of all other switches of the rectifier is in the off state, and the corresponding direct current voltage is u_dc＝2u_acThe mean DC average voltage is

u_dc＝2(u_abd_α+u_acd_β)；

7. A modulation method of a diode-clamped three-level high-voltage matrix converter according to claim 5 or 6, characterized in that the modulation signals of the inverter are:

therein, is disclosedThe inverter before normalization modulates the signal as

\{\begin{matrix} u_{Ao} = u_{A}^{*} + u_{no} \\ u_{Bo} = u_{B}^{*} + u_{no} \\ u_{Co} = u_{C}^{*} + u_{no} \end{matrix},

Wherein,

u_{no} = - \frac{\min {u_{A}^{*}, u_{B}^{*}, u_{C}^{*}} + \max {u_{A}^{*}, u_{B}^{*}, u_{C}^{*}}}{2}

is a zero-sequence signal and is used as a zero-sequence signal,

is the desired output voltage.