CN113452240B - Single-stage dual-mode three-port power electronic converter - Google Patents

Abstract

The invention relates to a single-stage dual-mode three-port power electronic converter, and belongs to the field of electronic devices. The single-stage dual-mode three-port power electronic converter comprises a direct-current side filter capacitor, four switching devices, two alternating-current side filter inductors, two alternating-current side filter capacitors and three output ports; the single-stage dual-mode three-port power electronic converter with simple topology and low cost can simultaneously output one path of direct current and one path of alternating current of different voltage grades or simultaneously output three paths of direct current electric energy of different voltage grades under the condition of only using one basic topology, has a simple and easy modulation method, and solves the problems of complex topology, high cost and low power density of the conventional multi-port power electronic converter.

Description

Single-stage dual-mode three-port power electronic converter

technical field

The invention belongs to the field of electronic devices, and relates to a single-stage dual-mode three-port power electronic converter.

Background technique

With the access of renewable energy power generation devices, energy storage equipment and other electrical energy and the diversification of demand for electrical equipment, traditional electrical energy conversion equipment cannot meet the requirements of the diversity of power supply forms. Therefore, multi-port power electronic converters emerge as the times require. It can provide different voltage levels and different types of electrical energy (direct current, alternating current) for the load. A multi-port power electronic converter refers to a power electronic transformer with multiple ports, generally having at least both AC and DC output ports at the same time. As a device that can realize multi-voltage levels and connect AC-DC hybrid distributed energy sources, the topology design and related control strategies of multi-port power electronic transformers are still in development. At present, the main ideas for designing multi-port power electronic converters are as follows: one or more basic power electronic topologies are connected in parallel or cascaded to obtain multiple channels of direct current and alternating current with different voltage levels at the same time. Although these schemes can output the required The output power quality can also be guaranteed. However, due to the use of multi-stage topology and a combination of multiple converter topologies, the volume and cost of the converter are increased, the power density is low, and a more complex control strategy is required.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a single-stage dual-mode three-port power electronic converter. For achieving the above object, the present invention provides the following technical solutions:

Single-stage dual-mode three-port power electronic converter, including DC-side filter capacitors, four switching devices, two AC-side filter inductors, two AC-side filter capacitors and three output ports;

The DC power supply is connected in parallel with the topology formed by the four switching devices after the DC side filter capacitor. The connection of the four switching devices is as follows: the switching device 1 and the switching device 2 are connected in series to form a phase-a bridge arm, and the switching device 3 and the switching device 4 are connected in series to form a bridge arm. For the b-phase bridge arm, the midpoint of the a-phase bridge arm is connected in series with the AC side filter inductor L ₁ to form terminal 1; the midpoint of the b-phase bridge arm is connected in series with the AC side filter inductor L ₂ to form terminal 2; the negative electrode of the DC side filter capacitor forms Terminal 3; An AC side filter capacitor C ₁ is connected in parallel between Terminal 1 and Terminal 3, and an AC side filter capacitor C ₂ is connected in parallel between Terminal 2 and Terminal 3; Terminal 1 and Terminal 2 form output port 12, Terminal 2 and Terminal 3 The output port 23 is constituted, and the terminal 1 and the terminal 3 constitute the output port 13 .

Optionally, the switch state of the bridge arm is a binary function S _i , i=a, b, where S _i =1 indicates that the switch tube T _i1 corresponding to the i-phase bridge arm is turned on, and S _i =0 indicates that the corresponding i-phase is turned on. The switch tube T _i2 of the bridge arm is turned on;

When the switch state of the i-phase bridge arm is 1, the bridge arm output voltage v _i =V _dc ;

When the switch state of the bridge arm of the i-phase is 0, the output voltage of the bridge arm v _i =0.

Optionally, the V ₁ is the voltage output by the a-phase bridge arm, V ₂ is the voltage output by the b-phase bridge arm, and the output voltage V ₁₂ of the converter port 12 is equal to the subtraction of the voltages of the two-phase bridge arms; The output voltage is expressed as:

V ₁₂ =V ₁ -V ₂

Under all possible switching sequences, the output of the converter is:

When the switch state is (1 1), the output voltages of port 12, port 13 and port 23 of the converter are 0, V _dc and V _dc respectively;

When the switch state is (0 0), the output voltages of port 12, port 13 and port 23 of the converter are 0, 0 and 0 respectively;

When the switch state is (1 0), the output voltages of port 12, port 13 and port 23 of the converter are V _dc , V _dc and 0 respectively;

When the switch state is (0 1), the output voltages at port 12, port 13 and port 23 of the converter are -V _dc , 0 and V _dc , respectively.

Optionally, the expression of the output voltage V _i of the i-phase bridge arm is:

The output voltage expression of converter port 12 is expressed as:

The time that the _i -phase bridge arm is in state 1 is defined as the duty cycle _Di , and the expression of Di is as follows:

Obtain the relationship between DC input voltage, duty cycle, and AC side output:

If the goal of the converter is to output a sinusoidal AC voltage, set the reference signal V _ref =V _m cos(θ); define the modulation index m, which represents the amplitude of the output voltage of the converter normalized by the DC side voltage V _dc , At the same time, m=V _m /V _dc , and then let v _m =mcos(θ), the formula becomes:

If the duty cycle of the two bridge arms satisfies the above relationship, the output voltage of the converter port 12 is equal to the target voltage V _ab , D _a and D _b are regarded as the modulation signals of the a-phase bridge arm and the b-phase bridge arm, v _m is regarded as a per-unit output voltage; according to the above principles, different a-phase modulation signals and b-phase modulation signals are defined to achieve different modes and different outputs.

Optionally, the different modes include mode one and mode two:

The first mode is: outputting one channel of direct current and one channel of alternating current at the same time;

The expressions that define the a-phase modulation signal and the b-phase modulation signal are as follows,

D _a =k+m·cos(θ), 0≤k≤1,0≤m≤min(k,1-k)

D _b = k

After the output is filtered by inductance and capacitance, an alternating current with an amplitude of m is obtained at port 12, and a direct current with an amplitude of k is obtained at port 23;

The second mode is: output three-way DC power at the same time;

D _a = a

D _b =b, 0≤b≤1, 0≤a≤1

After the output is filtered by the inductor and capacitor, the direct current of (ab)V _dc is obtained at port 12, the direct current of bV _dc is obtained at port 23, and the direct current of aV _dc is obtained at port 13.

The beneficial effect of the present invention is that: the single-stage dual-mode three-port power electronic converter with simple topology and low cost of the present invention can simultaneously output one channel of direct current and one channel of different voltage levels under the condition that only one basic topology is used. Alternating current, or outputting three-way direct current power with different voltage levels at the same time, and the modulation method is simple and easy to implement, which solves the problems of complex topology, high cost and low power density of current multi-port power electronic converters.

Other advantages, objects, and features of the present invention will be set forth in the description that follows, and will be apparent to those skilled in the art based on a study of the following, to the extent that is taught in the practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the following description.

Description of drawings

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be preferably described in detail below with reference to the accompanying drawings, wherein:

Figure 1 is a single-stage dual-mode three-port converter topology;

Fig. 2 is an embodiment of the present invention;

Fig. 3 is the mode one modulation mode;

Fig. 4 is the modulation mode of mode two;

Fig. 5 is the simulation result of mode one;

Figure 6 shows the simulation results of mode two.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments are only used to illustrate the basic idea of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

Among them, the accompanying drawings are only used for exemplary description, and represent only schematic diagrams, not physical drawings, and should not be construed as limitations of the present invention; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings will be omitted, The enlargement or reduction does not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the accompanying drawings may be omitted.

The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms “upper”, “lower”, “left” and “right” , "front", "rear" and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must be It has a specific orientation, is constructed and operated in a specific orientation, so the terms describing the positional relationship in the accompanying drawings are only used for exemplary illustration, and should not be construed as a limitation of the present invention. situation to understand the specific meaning of the above terms.

The basic structure of the present invention is shown in Figure 1, which includes a DC side filter capacitor connected in parallel with the DC side in a topology composed of four switching devices. The bridge arm, the switch device three and the switch device four are connected in series to form a b-phase bridge arm, the midpoint of the a-phase bridge arm is connected in series with the AC side filter inductance L ₁ to form terminal 1; the middle point of the b-phase bridge arm and the AC side filter inductance L ₂ Connect in series to form terminal 2; the negative electrode of the DC side filter capacitor forms terminal 3. An AC side filter capacitor C ₁ is connected in parallel between the terminal 1 and the terminal 3, and an AC side filter capacitor C ₂ is connected in parallel between the terminal 2 and the terminal 3. The terminal 1 and the terminal 2 constitute the output port 12 , the terminal 2 and the terminal 3 constitute the output port 23 , and the terminal 1 and the terminal 3 constitute the output port 13 . By setting different modulation modes, the product of the present invention can output AC power at port 12 and DC power at port 23, or output three-way DC power at the same time at port 12, port 23 and port 13 to meet different electricity demand.

The switching state of each bridge arm is defined as a binary function Si ( _i =a,b), where Si =1 indicates that the switch tube T _i1 corresponding to the _i -phase bridge arm is turned on, and Si =0 indicates that the corresponding _i -phase bridge arm is turned on The switch tube T _i2 is turned on. Analysis of the working process of the converter shows that when the switch state of the i-phase bridge arm is 1, the bridge arm output voltage v _i =V _dc ; when the i-phase bridge arm switch state is 0, the bridge arm output voltage v _i =0.

Definition V ₁ is the voltage output by the a-phase bridge arm, V ₂ is the output voltage of the b-phase bridge arm, and the output voltage V _ab of the converter is equal to the subtraction of the voltages of the two-phase bridge arms. Then the output voltage of the converter port 12 can be expressed as:

V ₁₂ =V ₁ -V ₂

Based on the above analysis, the output of the converter port 12 is summarized in Table 1 under all possible switching sequences.

Table 1 Output voltages corresponding to different switching sequences

(S_aS_b) (11) (00) (10) (01) V₁ V_dc 0 V_dc 0 V₂ V_dc 0 0 V_dc V₁₂ 0 0 V_dc -V_dc

The essence of PWM modulation is to make the average value of the output voltage in each switching cycle equal to the expected voltage value. The expression of the output voltage V _i of the i (i=a, b) phase bridge arm is as follows,

So the output voltage expression of converter port 12 can be expressed as:

The time when the i-phase bridge arm is in state 1 is defined as the duty cycle D _i (i=a, b). Through the above analysis, the expression of D _i can be obtained as follows:

Combining the above definitions, the relationship between the DC input voltage, duty cycle and AC side output can be obtained:

If the goal of the converter is to output a sinusoidal AC voltage, assume the reference signal V _ref =V _m cos(θ). Define the modulation index m, which represents the amplitude of the output voltage of the converter normalized by the DC side voltage V _dc , at the same time, m=V _m /V _dc , and then let v _m =mcos(θ), the formula changes at this time for:

As long as the duty cycle of the two bridge arms satisfies the above relationship, the output voltage of the converter is equal to the target voltage V _ab . At this time, D _a and D _b can be regarded as the modulation signals of the a-phase bridge arm and the b-phase bridge arm, _vm can be regarded as the per-unitized output voltage. According to the above principles, by defining different a-phase modulation signals and b-phase modulation signals, different modes and different outputs can be realized.

Mode 1: Simultaneous output of one direct current and one alternating current

The expressions that define the a-phase modulation signal and the b-phase modulation signal are as follows,

D _a =k+m·cos(θ)(0≤k≤1,0≤m≤min(k,1-k))

D _b =k(0≤k≤1)

At this time, after the output is filtered by the inductance and capacitance, the alternating current with the amplitude of m can be obtained at the port 12, and the direct current with the amplitude of k can be obtained at the port 23.

Mode 2: Simultaneous output of three channels of DC power

D _a =a (0≤a≤1)

D _b =b(0≤b≤1)

At this time, after the output is filtered by the inductor and capacitor, the direct current of (ab)V _dc can be obtained at the port 12, the direct current of bV _dc can be obtained at the port 23, and the direct current of aV _dc can be obtained at the port 13.

As shown in Fig. 2, the present invention can be used in a three-port converter of a microgrid. The electrical energy generated by distributed power sources such as photovoltaic cells and fans is direct current, and the present invention can convert the direct current generated by these distributed power sources into required electrical energy. When the user's electrical equipment includes a DC load or an AC load at the same time, the present invention works in mode 1 to provide alternating current and direct current at the same time. When the user's electrical equipment includes three or less DC loads with different power levels, the present invention Work in mode 2 to output three DC powers at the same time.

FIG. 3 is the modulation mode of mode one; FIG. 4 is the modulation mode of mode two; FIG. 5 is the simulation result of mode one; and FIG. 6 is the simulation result of mode two.

At present, multi-port power electronic converters mostly use the basic topology parallel and cascading methods to obtain different voltage levels and different types of voltages at the same time. Such methods often have more components, larger volume and higher cost. The present invention Only one basic topology is used, and by setting different modulation methods, multiple channels of different grades and types of electric energy can be obtained at the same time, using fewer components, lower cost, and higher power density.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be Modifications or equivalent replacements, without departing from the spirit and scope of the technical solution, should all be included in the scope of the claims of the present invention.

Claims (2)

1. A single-stage dual-mode three-port power electronic converter is characterized in that: comprising a DC side filter capacitor, four switching devices, two AC side filter inductors, two AC side filter capacitors and three output ports; The DC power supply is connected in parallel with the topology formed by the four switching devices after the DC side filter capacitor. The connection of the four switching devices is as follows: the switching device 1 and the switching device 2 are connected in series to form a phase-a bridge arm, and the switching device 3 and the switching device 4 are connected in series to form a bridge arm. For the b-phase bridge arm, the midpoint of the a-phase bridge arm is connected in series with the AC side filter inductor L ₁ to form terminal 1; the midpoint of the b-phase bridge arm is connected in series with the AC side filter inductor L ₂ to form terminal 2; the negative electrode of the DC side filter capacitor forms Terminal 3; An AC side filter capacitor C ₁ is connected in parallel between Terminal 1 and Terminal 3, and an AC side filter capacitor C ₂ is connected in parallel between Terminal 2 and Terminal 3; Terminal 1 and Terminal 2 form output port 12, Terminal 2 and Terminal 3 The output port 23 is constituted, and the terminal 1 and the terminal 3 constitute the output port 13; The switch state of the bridge arm is a binary function S _i , i=a,b, wherein S _i =1 means the switch tube T _i1 corresponding to the i-phase bridge arm is turned on, and S _i =0 means the switch corresponding to the i-phase bridge arm The tube T _i2 is turned on; When the switch state of the i-phase bridge arm is 1, the bridge arm output voltage v _i =V _dc ; When the switch state of the i-phase bridge arm is 0, the bridge arm output voltage v _i =0; V ₁ is the voltage output by the a-phase bridge arm, V ₂ is the voltage output by the b-phase bridge arm, and the output voltage V ₁₂ of the converter port 12 is equal to the subtraction of the voltages of the two-phase bridge arms; the output voltage of the converter is expressed as: V ₁₂ =V ₁ -V ₂ Under all possible switching sequences, the output of the converter is: When the switch state is (1 1), the output voltages of port 12, port 13 and port 23 of the converter are 0, V _dc and V _dc respectively; When the switch state is (0 0), the output voltages of port 12, port 13 and port 23 of the converter are 0, 0 and 0 respectively; When the switch state is (1 0), the output voltages of port 12, port 13 and port 23 of the converter are V _dc , V _dc and 0 respectively; When the switch state is (0 1), the output voltages of port 12, port 13 and port 23 of the converter are -V _dc , 0 and V _dc respectively; The expression of the output voltage V _i of the i-phase bridge arm is:

The output voltage expression of converter port 12 is expressed as:

The time that the _i -phase bridge arm is in state 1 is defined as the duty cycle _Di , and the expression of Di is as follows:

Obtain the relationship between DC input voltage, duty cycle, and AC side output:

The goal of the converter is to output a sinusoidal AC voltage, set the reference signal V _ref =V _m cos(θ); define the modulation index m, which represents the amplitude of the output voltage of the converter normalized by the DC side voltage V _dc , and at the same time , m=V _m /V _dc , then let v _m =mcos(θ), the formula becomes:

If the duty cycle of the two bridge arms satisfies the above relationship, the output voltage of the converter port 12 is equal to the target voltage V _ab , D _a and D _b are regarded as the modulation signals of the a-phase bridge arms and the b-phase bridge arms, v _m is regarded as the per-unit output voltage; according to the above principles, different a-phase modulation signals and b-phase modulation signals are defined to achieve different modes and different outputs. 2. The single-stage dual-mode three-port power electronic converter according to claim 1, wherein the different modes include mode one and mode two: The first mode is: outputting one channel of direct current and one channel of alternating current at the same time; The expressions that define the a-phase modulation signal and the b-phase modulation signal are as follows, D _a =k+m·cos(θ), 0≤k≤1,0≤m≤min(|k|,1-k) D _b = k After the output is filtered by inductance and capacitance, an alternating current with an amplitude of m is obtained at port 12, and a direct current with an amplitude of k is obtained at port 23; The second mode is: output three-way DC power at the same time; D _a = a D _b =b, 0≤b≤1, 0≤a≤1 After the output is filtered by the inductor and capacitor, the direct current of (ab)V _dc is obtained at port 12, the direct current of bV _dc is obtained at port 23, and the direct current of aV _dc is obtained at port 13.

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