CN104601002B - A kind of sparse formula dual stage matrix converter topological structure - Google Patents

Abstract

The invention discloses a novel sparse dual-stage matrix converter topological structure, which comprises the following parts: three bidirectional controllable switches, a three-phase diode rectifier bridge and a three-phase inverter. The invention avoids the disadvantage that the rectification stage of other two-stage matrix converters is prone to generate negative pressure and then short-circuit fault, and can effectively improve system reliability. In addition, the invention can also expand the adjustment range of input reactive power angle to [‑90°, 90°], which solves the problem that the input side power factor angle of traditional two-stage matrix converter can only be in [‑30°, 30°] ] The problem of adjustment within the range; the topology of the present invention, the control is simple and reliable, and has high practical value.

Description

A Sparse Two-Stage Matrix Converter Topology

technical field

The invention relates to an electric energy conversion device, in particular to a novel sparse dual-stage matrix converter topology.

Background technique

Matrix converter is a new type of AC-AC converter, which has the characteristics of small size, light weight and long working life. It is regarded as one of the alternative topologies of dual PWM converters that are widely used at present, and has been widely studied at home and abroad. . The two-stage matrix converter is a subclass of the matrix converter, including two parts of the rectification stage and the inverter stage. The two parts are connected through the DC intermediate DC bus, but there is no DC energy storage element. Compared with the traditional matrix converter, the two-stage matrix converter has the advantages of simple clamping circuit and easy implementation of commutation control strategy, which has attracted extensive attention of researchers.

When the system does not require the converter to have bidirectional power flow capability, the two-stage matrix converter can also reduce the number of switches, and it is called a sparse two-stage matrix converter at this time. A typical traditional sparse two-stage matrix converter topology is shown in Figure 1. The rectification stage consists of six fully controlled devices (each containing a body diode) and six additional diodes. It has the same functions as traditional matrix converters and dual-stage matrix converters except that it cannot realize bidirectional power flow.

However, like the common two-stage matrix converter, the structure shown in Fig. 1 has a big defect. Its rectification stage consists of fully controlled devices that may generate negative DC bus voltages. For example, when the input three-phase voltage satisfies: u _A > u _B > u _C , if the fully-controlled devices of the upper bridge arm of phase C and the lower bridge arm of phase A of the rectification stage are turned on, the DC bus voltage u _dc = u _C - u _A <0. At this time, because the diodes of each bridge arm of the inverter stage cannot block the negative voltage, a short-circuit fault will occur, endangering the safety of the system. This situation is common in practical systems, such as input-side oscillation and electromagnetic interference, which cause false conduction of the full control device of the rectification stage. More importantly, it has been proved by literature that when the input power factor angle is greater than 30° or less than -30°, the DC bus voltage will inevitably have a negative value. Therefore, the above defects also limit the input power factor angle of the traditional sparse matrix converter to [-30°, 30°], which affects the reactive power adjustment function of the converter.

Contents of the invention

Technical problems to be solved:

The purpose of the present invention is to provide a novel sparse dual-stage matrix converter topology that can avoid negative pressure in the rectification stage.

Technical solutions:

In order to realize the above functions, the present invention provides a novel sparse dual-stage matrix converter topology, which is characterized in that it includes three bidirectional switches, a rectifier stage and an inverter stage;

Among them, the rectification stage includes six diodes, and the inverter stage includes six fully-controlled devices. The input three-phase AC voltage (u _A , u _B , u _C ) is respectively connected to the rectifier through bidirectional switch S1, bidirectional switch S2, and bidirectional switch S3. The three-phase AC terminal of the rectification stage is connected to the DC bus of the inverter stage, and the output three-phase AC voltage (u _U , u _V , u _W ) is connected to the three-phase AC end of the inverter stage.

Each bidirectional switch is composed of two fully-controlled devices with a common emitter, and each fully-controlled device is connected in parallel with a reverse body diode.

The two fully controlled devices of each bidirectional switch use the same PWM control signal, the duty cycle of bidirectional switch S1 is d ₁ , the duty cycle of bidirectional switch S2 is d ₂ , and the duty cycle of bidirectional switch S3 is d ₃ , which are determined by:

Among them, |u _A |, |u _B |, |u _C | represent the absolute values of three-phase input voltages u _A , u _B , u _C respectively, and u _imax represents |u _A |, |u _B |, |u _C |The maximum value in .

In each bidirectional switch period, the bidirectional switch of the phase whose absolute value of the input voltage is equal to u _imax is constantly turned on, and the bidirectional switches of the other two phases are turned on alternately according to their corresponding duty ratios.

Beneficial effect:

It can be seen from the above-mentioned technical scheme that the novel sparse dual-stage matrix converter topology provided by the present invention has the following beneficial effects compared with the prior art:

1. In the present invention, the rectification stage will not generate negative voltage under any circumstances, and no short-circuit fault will occur through the bridge arm diode of the inverter stage, which is very conducive to improving the reliability of the system;

2. The present invention can also expand the angle adjustment range of the input power factor to [-90°, 90°], breaking through the original two-stage matrix converter that can only adjust the input power factor within the range of [-30°, 30°] Angular limitations;

3. In the present invention, the control of the three bidirectional switches is very convenient, the calculation of the duty ratio is simple, and no dead time needs to be set during the commutation.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention is further described:

Figure 1 is a typical traditional sparse matrix converter topology;

A kind of novel sparse type two-stage matrix converter topology that Fig. 2 present invention proposes;

The structural diagram of the composition of the bidirectional switch of Fig. 3;

Figure 4. Duty ratio expressions of three bidirectional switches in one input voltage cycle;

Figure 5 is a driving waveform diagram of three bidirectional switches in one switching cycle (u _A >0>u _B >u _C ).

detailed description

The present invention provides a novel sparse dual-stage matrix converter topology. In order to make the object, technical solution and effect of the present invention clearer and clearer, the present invention will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific implementations described here are only used to explain the present invention, not to limit the present invention.

The system structure proposed by the present invention is shown in Figure 2. The three-phase input voltage (u _A , u _B , u _C ) is respectively connected to the input terminal of the rectification stage through three bidirectional switches (S1, S2, S3). The rectification stage is composed of six diodes. The DC bus bars of the inverter stages are connected, and the inverter stage is composed of an ordinary three-phase inverter, and the three-phase output voltage (u _U , u _V , u _W ) is connected to the three-phase AC terminal of the inverter stage. In Figure 2, the three bidirectional switches are four-quadrant switches, which can flow bidirectional current and block bidirectional voltage. The bidirectional switch structure adopted in the present invention is shown in Fig. 3, each bidirectional switch is formed by two full-control devices (including body diodes) connected in series with common emitters. Choosing such a bidirectional switch can reduce the number of isolated driving power supplies, simplify the design of the driving circuit, and reduce the stray inductance of the line.

Three bidirectional switches S1, S2, and S3 are turned on in pairs to generate an effective switch combination. There are three combinations in total, as shown in Table 1. For example, when the switches S1 and S2 are turned on and S3 is turned off, the DC bus voltage u _dc = |u _A -u _B |, where the absolute value symbol || represents the full-wave rectification effect of the rectifier stage diode. When S1, S2, and S3 are all turned on, the rectification stage is an ordinary three-phase full-wave rectification, and the DC bus voltage is any one of the three voltages in Table 1, so this combination is not an effective switch combination. When only one switch among S1 , S2 , and S3 is turned on or none of the switches is turned on, the DC bus voltage is 0, so it is not an effective combination of switches. It can be seen from Table 1 that no matter what the three-phase input voltage is, the DC bus voltage can be selected as any one of the three line voltages. This characteristic is necessary for all matrix converters to realize sinusoidal input. Therefore, the structure shown in the present invention can also realize the sinusoidalization of the input current.

Table 1 The relationship between the conduction state of the three bidirectional switches and the DC bus voltage

S1 S2 S3 turn on turn on turn off turn on turn off turn on turn off turn on turn on

It can also be seen from Figure 2 and Table 1 that since the rectification stage is composed of diodes, the unidirectional conduction characteristics of the diodes make the DC bus voltage must be positive. Therefore, regardless of the control of the three bidirectional switches on the input line, the rectification stage will not generate negative voltage, and thus will not cause short circuit failure. In particular, if the three bidirectional switches are turned on at the same time, the entire topology can be equivalent to the connection between the diode uncontrolled rectifier bridge and the inverter, and the input three-phase short-circuit fault will not occur. This situation will cause phase-to-phase short circuit in traditional matrix converters, dual-stage matrix converters and traditional sparse dual-stage matrix converters, resulting in overcurrent and endangering the safety of power devices.

The characteristic that the DC bus voltage must be positive also enables the input power factor angle to be adjusted arbitrarily within the range of [-90°, 90°]. In other two-stage matrix converters, when the input power factor angle is not in the range [-30°, 30°], the DC bus voltage will appear negative, causing a short circuit fault. In the topology of the present invention, even if the input power factor angle is not [-30°, 30°], the rectification function of the rectification stage ensures that the DC bus voltage will not appear negative. Therefore, the present invention has a wider power factor angle adjustment range than other dual-stage matrix converters.

The topology control method shown in Figure 2 is also very simple, and the inverter stage can use the traditional voltage space vector modulation algorithm. Different from other matrix converters, the present invention has only three bidirectional switches, which only need three PWM control signals (two full-control devices of each bidirectional switch can share one PWM control signal). To ensure the sinusoidal degree of the input current, the duty cycles of the three bidirectional switches are determined by the following equations:

In the formula, d ₁ , d ₂ , and d ₃ are the duty ratios of bidirectional switches S1, S2, and S3 respectively, and |u _A |, |u _B |, |u _C | represent the three-phase input voltages u _A , u _B , the absolute value of u _C , u _imax represents the maximum value among |u _A |, |u _B |, |u _C |. Accompanying drawing 4 is the expression of d ₁ , d ₂ and d ₃ within a power supply voltage cycle. In this kind of control mode, the current flowing through each phase of the input voltage is proportional to the absolute value of the voltage. This is the same characteristic as other matrix converters, so this control method guarantees the sinusoidal degree of the input current. When u _A >0 >u _B >u _C , within one switching cycle, the driving waveforms of S1, S2, and S3 are shown in Fig. 5 . When three-phase voltages u _A , u _B and u _C are input, a similar analysis can also be performed. In Figure 5, T _s represents the switching period, "1" represents the corresponding switch is on, "0" represents the corresponding switch is off, d ₂ T _s represents the time when the bidirectional switch S2 is on, and d ₃ T _s represents the bidirectional switch S3 turn-on time. It can be seen from the figure that at this time, the bidirectional switch S1 is constantly turned on in one switching cycle, and the bidirectional switches S2 and S3 are turned on alternately. When the conduction states of S2 and S3 are switched, their driving signals do not need to set a dead zone. This is because, even if S2 and S3 are turned on at the same time, due to the unidirectional conduction characteristic of the diode in the rectification stage, the input phase B and C phase will not be short-circuited. This characteristic is also another advantage of the topology of the present invention over other dual-stage matrix converter topologies.

It can be understood that those skilled in the art can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention, and all these changes or replacements should belong to the protection scope of the appended claims of the present invention.

Claims (2)

1. A sparse dual-stage matrix converter topology is characterized in that: it includes three bidirectional switches, a rectification stage and an inverter stage; wherein the rectification stage includes six diodes, and the inverter stage includes six fully-controlled devices, The input three-phase AC voltage (u _A , u _B , u _C ) is respectively connected to the three-phase AC terminal of the rectification stage through the bidirectional switch S1, bidirectional switch S2, and bidirectional switch S3, and the DC bus of the rectification stage and the DC bus of the inverter stage Connected, the output three-phase AC voltage (u _U , u _V , u _W ) is connected to the three-phase AC terminal of the inverter stage; each bidirectional switch is composed of two fully-controlled devices with common emitters, each fully-controlled The device is connected in parallel with a reverse body diode; the two fully-controlled devices of each bidirectional switch use the same PWM control signal, the duty cycle of the bidirectional switch S1 is d ₁ , the duty cycle of the bidirectional switch S2 is d ₂ , and the bidirectional switch The duty cycle of S3 is d ₃ , which are determined by: $\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; |</span>}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}\\ {\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; |</span>}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; max</span>}}}\\ {\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; |</span>}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}\end{array}\right.$ Among them, |u _A |, |u _B |, |u _C | represent the absolute values of three-phase input voltages u _A , u _B , u _C respectively, and u _imax represents |u _A |, |u _B |, |u _C |The maximum value in . 2. The topology structure of a kind of sparse dual-stage matrix converter according to claim 1, characterized in that: in each bidirectional switching period, the bidirectional switch of the phase whose absolute value of the input voltage is equal to u _imax is constantly turned on , the bidirectional switches of the remaining two phases are turned on alternately according to their corresponding duty ratios.