Three-port power spring topology and fluctuation suppression method thereof

Abstract

The invention discloses a three-port power spring topology and a fluctuation suppression method thereof, and relates to a power spring topology and a fluctuation suppression method thereof. The problem that the service life of an energy storage device is shortened due to the fact that the energy storage device needs to be frequently switched for energy transfer is solved. According to the invention, double-phase-shift control is adopted, two control variables are provided, traditional single-phase-shift control is replaced, and the degree of freedom of an electric spring control mode is expanded, so that the control is more flexible. According to the method, the output power fluctuation can be actively inhibited under the condition that the battery does not work or a small amount of power is transmitted, so that the battery loss under the normal working condition is reduced. The method comprises full-range soft switching control, the controller can calculate the phase shift angle range, parallel capacitors of all switches are enabled to be completely discharged before driving pulses arrive, diodes of switch bodies conduct currents, zero-voltage switching is achieved, switching loss is reduced, and therefore high efficiency is guaranteed. The invention belongs to the technical field of power electronic converter modulation.

Description

Technical Field

[0001] The present invention relates to a power spring topology and its fluctuation suppression method, belonging to the technical field of power electronic converter modulation. Background Art

[0002] Future renewable energy power generation systems need to connect various energy sources such as energy storage batteries and photovoltaic modules with loads and backup batteries. Three-port converters have been applied in such systems because of their advantages such as reducing power transmission stages, high-frequency links, multi-winding transformers, and centralized control. Some of these applications are used in fuel cell systems, automobiles, and independent residential buildings. To avoid the above disadvantages of traditional power converters, scholars have proposed and extended the concept of three-port electrical springs.

[0003] Currently, the control of three-port electrical springs generally includes the modulation of three-active-bridge converters and energy storage batteries. The three-active-bridge converter is an extension of the dual-active-bridge converter topology, and its control strategy is similar to that of the dual-active-bridge converter, which can be divided into single-phase-shift control, double-phase-shift control, and triple-phase-shift control. Currently, the control strategy of three-active-bridge converters focuses more on the decoupling of single-phase-shift control to achieve power regulation and efficiency improvement. However, single-phase-shift control has problems such as a large primary circuit power, low efficiency, and a small soft-switching region under high voltage gain. During the power fluctuation of the microgrid, the three-active-bridge can transfer the fluctuation to non-critical loads, thus ensuring the power quality of critical loads. When the power fluctuation on the output side of the microgrid is large, non-critical loads cannot fully absorb the input power fluctuation. At this time, the energy storage device needs to discharge to maintain power stability. To ensure the stability of the output voltage and the balance of the system instantaneous power, the energy storage device needs to switch frequently to transfer energy, which poses a severe test to the life of the energy storage device. Therefore, the research on three-port power spring topology and its optimized control strategy is very meaningful. Summary of the Invention

[0004] In order to solve the problem that the energy storage device needs to switch frequently to transfer energy, resulting in a shortened life of the energy storage device, the present invention further provides a three-port power spring topology and its fluctuation suppression method.

[0005] The technical solution adopted by the present invention to solve the above problems is that a three-port power spring topology described in the present invention includes an inverter full-bridge circuit, a cycloconverter, a full-bridge rectifier, a DC input power supply, a power inductor, a high-frequency transformer T r , a load, an energy storage battery, and a bidirectional buck-boost converter;

[0006] The inverter full-bridge circuit, the cycloconverter, and the full-bridge rectifier are arranged in a triangular shape. The DC input power supply is sequentially connected in series with the inverter full-bridge circuit, the power inductor, and the high-frequency transformer T r, a cycloconverter and a full - bridge rectifier. The full - bridge rectifier is connected to the critical terminal of the load, and the cycloconverter is connected to the non - critical terminal of the load;

[0007] High - frequency transformer T r One end of the tertiary side in T is connected to the mid - point of the first bridge arm of the full - bridge rectifier. High - frequency transformer T r The other end of the tertiary side in T is connected to the mid - point of the second bridge arm of the full - bridge rectifier;

[0008] The energy - storage battery is connected to both ends of the load through a bidirectional buck - boost converter.

[0009] Furthermore, the inverter full - bridge circuit includes a first switching tube S1, a second switching tube S2, a third switching tube S3, and a fourth switching tube S4;

[0010] One end of the first switching tube S1 and the third switching tube S3 are connected to the positive pole of the DC input power supply, and one end of the second switching tube S2 and the fourth switching tube S4 are connected to the negative pole of the DC input power supply;

[0011] High - frequency transformer T r is connected to the input end of the power inductor. The other end of the third switching tube S3 is connected to the other end of the fourth switching tube S4 and high - frequency transformer T r and connected.

[0012] Furthermore, the cycloconverter includes a fifth switching tube S5, a sixth switching tube S6, a seventh switching tube S7, an eighth switching tube S8, a ninth switching tube S9, a tenth switching tube S 10 , an eleventh switching tube S 11 and a twelfth switching tube S 12 ;

[0013] The fifth switching tube S5, the sixth switching tube S6, the seventh switching tube S7, the eighth switching tube S8, the ninth switching tube S9, the tenth switching tube S 10 , the eleventh switching tube S 11 and the twelfth switching tube S 12 are connected in a common - source configuration.

[0014] Furthermore, the full - bridge rectifier is composed of a thirteenth switching tube S 13 , a fourteenth switching tube S 14 , a fifteenth switching tube S 15 and a sixteenth switching tube S 16 .

[0015] Furthermore, the first switching tube S1, the second switching tube S2, the third switching tube S3, the fourth switching tube S4, the fifth switching tube S5, the sixth switching tube S6, the seventh switching tube S7, the eighth switching tube S8, the ninth switching tube S9, the tenth switching tube S 10 , the eleventh switching tube S11 and the twelfth switching transistor S 12 and the thirteenth switching transistor S 13 and the fourteenth switching transistor S 14 and the fifteenth switching transistor S 15 and the sixteenth switching transistor S 16 are all SiC MOSFETs.

[0016] The steps of the three-port power spring ripple suppression method described in the present invention include:

[0017] Step 1: In the critical load voltage control, the tertiary side voltage u3 is used as the controlled quantity, and the phase shift angle ε 13 is obtained by subtracting u3 from the critical load reference voltage u 3，ref and then passing through a PI controller, and it is limited between 0 and 90°;

[0018] Step 2: In the non-critical load voltage control, the secondary side voltage u2 is used as the controlled quantity, and the phase shift angle ε 12 is obtained by subtracting u2 from the non-critical load reference voltage u 2，ref and then passing through a PI controller, and it is limited between 0 and 90°;

[0019] Step 3: In the energy storage battery control, when the energy storage unit starts to work, u C4 is input into a PI controller to obtain the duty cycle D of the buck-boost converter, and its value range is between 0 and 1.

[0020] Furthermore, M 12 is the voltage conversion ratio M between the primary side and the secondary side 12 = u2 / nu1, and M 13 is the voltage conversion ratio M between the primary side and the tertiary side 13 = u3 / nu1;

[0021] The phase shift ratio satisfies the condition of zero voltage turn-on:

[0022]

[0023] The first switching transistor S1, the second switching transistor S2, the third switching transistor S3, the fourth switching transistor S4, the fifth switching transistor S5, the sixth switching transistor S6, the seventh switching transistor S7, the eighth switching transistor S8, the ninth switching transistor S9, the tenth switching transistor S 10 and the eleventh switching transistor S 11 and the twelfth switching transistor S 12 and the thirteenth switching transistor S 13 and the fourteenth switching transistor S 14 and the fifteenth switching transistor S 15 and the sixteenth switching transistor S 16 can all achieve zero voltage conduction.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The present invention uses double phase-shift control for the provided three-port power spring topology to expand the degree of freedom of the power spring control method, thereby making the control more flexible;

[0026] 2. When the three-port power spring control fluctuation suppression method provided by the present invention is specifically operated, it can actively suppress the output power fluctuation when the battery is not working or transmitting a small amount of power, thereby reducing the battery loss under normal working conditions;

[0027] 3. The three-port power spring topology and its fluctuation suppression method provided by the present invention include full-range soft-switching control. The controller can calculate the phase-shift angle range to completely discharge the parallel capacitance of all switches before the drive pulse, conduct the current of the body diode, achieve zero-voltage turn-on, and reduce the switching loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of the three-port power spring topology;

[0029] Figure 2 is the equivalent topology diagram of the three-port power spring topology;

[0030] Figure 3 is the schematic diagram of the three-port power spring fluctuation suppression method;

[0031] Figure 4 is the principle waveform diagram of the three-port power spring working state;

[0032] Figure 5 is the simulation waveform diagram of the output power of each port of the three-port power spring when the energy storage battery is not working;

[0033] Figure 6 is the simulation waveform diagram of the output power of each port of the three-port power spring when the energy storage battery is working;

[0034] Figure 7 is the simulation waveform diagram of the zero-voltage turn-on of the primary-side switch S1 of the three-port power spring;

[0035] Figure 8 is the simulation waveform diagram of the zero-voltage turn-on of the secondary-side switch S5 of the three-port power spring. DETAILED DESCRIPTION OF THE INVENTION

[0036] DETAILED DESCRIPTION OF THE INVENTION I: As Figure 1 shown, a three-port power spring topology includes an inverter full-bridge circuit, a cycloconverter, a full-bridge rectifier, a DC input power supply, a power inductor, and a high-frequency transformer T r, load, energy storage battery and bidirectional buck-boost converter;

[0037] The full-bridge inverter circuit, cycloconverter and full-bridge rectifier are arranged in a triangular pyramid shape. The DC input power supply is connected in series with the full-bridge inverter circuit, power inductor, high-frequency transformer T r , cycloconverter and full-bridge rectifier in sequence. The full-bridge rectifier is connected to the critical terminal of the load, and the cycloconverter is connected to the non-critical terminal of the load;

[0038] One end of the tertiary side of the high-frequency transformer T r is connected to the midpoint of the first bridge arm of the full-bridge rectifier, and the other end of the tertiary side of the high-frequency transformer T r is connected to the midpoint of the second bridge arm of the full-bridge rectifier;

[0039] The energy storage battery is connected to both ends of the load through a bidirectional buck-boost converter.

[0040] Among them, C1 is the primary side voltage stabilizing capacitor, u C1 is the voltage across the capacitor C1, C2 is the secondary side voltage stabilizing capacitor, u C2 is the voltage across the capacitor C2, C3 is the tertiary side voltage stabilizing capacitor, u C3 is the voltage across the capacitor C3. u C4 is the voltage stabilizing capacitor on the buck-boost converter side, u C4 is the voltage across the capacitor C4.

[0041] Among them, the full-bridge inverter circuit includes the first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4; one end of the first switch tube S1 and the third switch tube S3 are connected to the positive pole of the DC input power supply, and one end of the second switch tube S2 and the fourth switch tube S4 are connected to the negative pole of the DC input power supply; the high-frequency transformer T r is connected to the input end of the power inductor, and the other end of the third switch tube S3 is connected to the other end of the fourth switch tube S4 and the high-frequency transformer T r for connection.

[0042] Among them, the cycloconverter includes the fifth switch tube S5, the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9, the tenth switch tube S 10 , the eleventh switch tube S 11 and the twelfth switch tube S 12 ; the fifth switch tube S5, the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9, the tenth switch tube S 10 , the eleventh switch tube S 11 and the twelfth switch tube S 12 are connected using the common-source connection method.

[0043] Among them, the full-bridge rectifier is composed of the thirteenth switch tube S13 , the fourteenth switching transistor S 14 , the fifteenth switching transistor S 15 and the sixteenth switching transistor S 16 . The first switching transistor S1, the second switching transistor S2, the third switching transistor S3, the fourth switching transistor S4, the fifth switching transistor S5, the sixth switching transistor S6, the seventh switching transistor S7, the eighth switching transistor S8, the ninth switching transistor S9, the tenth switching transistor S 10 , the eleventh switching transistor S 11 , the twelfth switching transistor S 12 , the thirteenth switching transistor S 13 , the fourteenth switching transistor S 14 , the fifteenth switching transistor S 15 and the sixteenth switching transistor S 16 are all SiC MOSFETs.

[0044] As Figure 2 shown, L 13 is the equivalent inductance between the primary side and the tertiary side, L 12 is the equivalent inductance between the primary side and the secondary side, L 23 is the equivalent inductance between the secondary side and the tertiary side, i 12 is the current passing through L 12 , i 13 is the current passing through L 13 , i 23 is the current passing through L 23 . u'2 is the voltage across the non-critical load R NC , and u'3 is the voltage across the critical load R C . i1 is the primary side input current, i2 is the secondary side output current, and i3 is the tertiary side output current.

[0045] Specific Embodiment 2: As Figure 3 shown, a three-port power spring fluctuation suppression method, the specific steps include:

[0046] Step 1. In the critical load voltage control, the tertiary side voltage u3 is used as the controlled quantity, and the phase shift angle ε 13 is obtained by subtracting u3 from the critical load reference voltage u 3，ref and then passing through a PI controller, and it is limited between 0 and 90°;

[0047] Step 2. In the non-critical load voltage control, the secondary side voltage u2 is used as the controlled quantity, and the phase shift angle ε 12 is obtained by subtracting u2 from the non-critical load reference voltage u 2，ref and then passing through a PI controller, and it is limited between 0 and 90°;

[0048] Step 3. In the energy storage battery control, when the energy storage unit starts to work, u C4 is input into a PI controller to obtain the duty cycle D of the buck-boost converter, and its value range is between 0 and 1.

[0049] Among them, M 12 is the voltage conversion ratio between the primary side and the secondary side, M 12 = u2 / nu1, M 13 is the voltage conversion ratio between the primary side and the tertiary side, M 13 = u3 / nu1;

[0050] The phase shift ratio satisfies the condition of zero-voltage switching:

[0051]

[0052] The first switch tube S1, the second switch tube S2, the third switch tube S3, the fourth switch tube S4, the fifth switch tube S5, the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9, the tenth switch tube S 10 , the eleventh switch tube S 11 , the twelfth switch tube S 12 , the thirteenth switch tube S 13 , the fourteenth switch tube S 14 , the fifteenth switch tube S 15 and the sixteenth switch tube S 16 can all achieve zero-voltage conduction.

[0053] Among them, as Figure 4 shown, the calculation formula for the active power is:

[0054]

[0055] Among them, p 12 represents the power transmitted from the primary side to the secondary side, p 13 represents the power transmitted from the primary side to the tertiary side, p 23 represents the power transmitted from the secondary side to the tertiary side.

[0056] The requirement for achieving zero-voltage conduction is that the current before the switch conducts passes through the anti-parallel diode due to the energy storage of the inductor, thereby clamping the switch voltage to zero; according to symmetry, it is deduced that i1(t1) = -i1(t5); the condition for all switch tubes on the primary side to achieve zero-voltage conduction is i1(t1) < 0; similarly, the condition for all switch tubes on the secondary side to achieve zero-voltage conduction is i2(t2) < 0; the condition for all switch tubes on the tertiary side to achieve zero-voltage conduction is i3(t3) > 0; according to the above analysis, the zero-voltage conduction conditions for the three ports are as follows:

[0057]

[0058] Among them, M 12 represents the voltage conversion ratio M between the primary side and the secondary side 12 = u2 / nu1, M 13 represents the voltage conversion ratio M between the primary side and the tertiary side 13 = u3 / nu1;

[0059] Through the above relationships of power and current, and the phase-shift control principle, the conditions for achieving zero-voltage turn-on are obtained as follows:

[0060]

[0061] As Figure 5 shown, when the storage battery is not working, the DC bus voltage fluctuation range is ±10%; the photovoltaic power fluctuation time is set to 0.3 s and 0.6 s; at 0.3 s, the photovoltaic power suddenly changes from 156 W to 167 W; the power consumed by the non-critical end of the load changes from 76 W to 87 W; the energy storage battery does not charge or discharge. Therefore, when the photovoltaic-side power slightly increases, the proposed optimal control can not only keep the power of the critical load stable, but also realize the transfer of power fluctuation to the non-critical end of the load; the non-critical end of the load consumes more electric energy, avoiding the operation of the energy storage battery; the photovoltaic power changes from 167 W to 146 W within 0.6 s; the power consumed by the critical end of the load remains at 80 W, and the power consumed by the non-critical end of the load drops from 87 W to 66 W. Therefore, when the power of the photovoltaic cell slightly decreases, the designed control method can not only keep the stability of the power of the critical load end, but also transfer the input power fluctuation to the non-critical end of the load. The non-critical end of the load can reduce power consumption and avoid outputting electric energy from the battery.

[0062] As Figure 6 shown, when the storage battery is working, the DC bus voltage fluctuation range exceeds ±10%. The photovoltaic power fluctuation time is set to 0.3 s and 0.6 s. At 0.3 s, the photovoltaic power suddenly changes from 156 W to 206 W. The power consumed by the non-critical load changes from 76 W to 120 W. The output power of the energy storage battery rises to 6 W. Therefore, when the photovoltaic-side power slightly increases, the proposed optimal control can not only keep the power of the critical load stable, but also realize the transfer of power fluctuation to the non-critical load. The non-critical load consumes more electric energy, avoiding excessive output power of the energy storage battery. The photovoltaic power changes from 206 W to 106 W within 0.6 s. The power consumed by the critical load remains at 80 W, and the power consumed by the non-critical load drops from 120 W to 25 W. The energy storage battery changes from an output power of 6 W to an input power of 5 W. Therefore, when the power of the photovoltaic cell slightly decreases, the designed control method can not only keep the stability of the power of the critical load, but also transfer the input power fluctuation to the non-critical load. The non-critical load can reduce power consumption and avoid inputting too much electric energy from the battery.

[0063] As Figure 7 shown, i S1 is the current flowing through the switch S1, and v gs1 is the gate voltage of the switch S1, and v ds1 is the drain-source voltage of the switch S1. Before the switch turns on, the current passes through the anti-parallel diode due to the energy storage of the inductor, thus clamping the switch voltage to zero. This proves the correctness of the proposed control strategy in achieving zero-voltage turn-on of the primary-side switch.

[0064] As Figure 8 shown, i S5 is the current flowing through the switch S 15 , and v gs5 is the gate voltage of the switch S5, and v ds5 is the drain-source voltage of the switch S5. Before the switch turns on, the current passes through the anti-parallel diode due to the energy storage of the inductor, thus clamping the switch voltage to zero. This proves the correctness of the proposed control strategy in achieving zero-voltage turn-on of the secondary-side switch.

[0065] Due to the adoption of dual-phase-shift control, the circuit of the present invention has two control variables, ε 12 and ε 13 , instead of the traditional single-phase-shift control, which expands the degree of freedom of the power spring control method, making the control more flexible. The method can actively suppress the output power fluctuation when the battery is not working or transmitting a small amount of power, thereby reducing the battery loss under normal working conditions. The method includes full-range soft-switching control. The controller can calculate the range of the phase-shift angle, so that the parallel capacitors of all switches are completely discharged before the drive pulse, and the body diode conducts current to achieve zero-voltage turn-on and reduce the switch loss. The power spring control has a simple structure and obvious advantages, and has a wide application prospect.

[0066] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the equivalent embodiments by using the above-disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiments according to the technical essence of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A three-port power spring topology, characterized in that: Including inverter full-bridge circuit, cycloconverter, full-bridge rectifier, DC input power supply, power inductor, high-frequency transformer T r , load, energy storage battery and bidirectional buck-boost converter; The inverter full-bridge circuit, the cycloconverter and the full-bridge rectifier are arranged in a triangular shape. The DC input power supply is connected in series with the inverter full-bridge circuit, the power inductor, and the high-frequency transformer T r , a cycloconverter and a full-bridge rectifier, the full-bridge rectifier is connected to a critical end of the load, and the cycloconverter is connected to a non-critical end of the load; High frequency transformer T r One end of the tertiary side is connected to the midpoint of the first bridge arm of the full-bridge rectifier, and the high-frequency transformer T r The other end of the tertiary side is connected to the midpoint of the second bridge arm of the full-bridge rectifier; The energy storage battery is connected to both ends of the load through a bidirectional buck-boost converter.

2. A three-port power spring topology according to claim 1, characterized in that: The inverter full-bridge circuit includes a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4; One end of the first switch tube S1 and the third switch tube S3 are connected to the positive electrode of the DC input power supply, and one end of the second switch tube S2 and one end of the fourth switch tube S4 are connected to the negative electrode of the DC input power supply; High frequency transformer T r The other end of the third switch tube S3 is connected to the other end of the fourth switch tube S4 and the high frequency transformer T r connect.

3. A three-port power spring topology according to claim 1, characterized in that: The cycloconverter includes a fifth switch tube S5, a sixth switch tube S6, a seventh switch tube S7, an eighth switch tube S8, a ninth switch tube S9, a tenth switch tube S 10 , Eleventh switch tube S 11 and the twelfth switch tube S 12 ; The fifth switch tube S5, the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9, the tenth switch tube S 10 , Eleventh switch tube S 11 and the twelfth switch tube S 12 Use common source connection.

4. A three-port power spring topology according to claim 1, characterized in that: The full-bridge rectifier consists of the thirteenth switch tube S 13 , the fourteenth switch tube S 14 , the fifteenth switch tube S 15 and the sixteenth switch tube S 16 composition.

5. A three-port power spring topology according to claim 1, 2, 3 or 4, characterized in that: The first switch tube S1, the second switch tube S2, the third switch tube S3, the fourth switch tube S4, the fifth switch tube S5, the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9, the tenth switch tube S 10 , Eleventh switch tube S 11 , the twelfth switch tube S 12 , Thirteenth switch tube S 13 , the fourteenth switch tube S 14 , the fifteenth switch tube S 15 and the sixteenth switch tube S 16 Both are SiC MOSFETs.

6. A three-port power spring fluctuation suppression method, characterized in that: The specific steps include: Step 1: In the critical load voltage control, the tertiary voltage u3 is used as the controlled variable, and the phase shift angle ε 13 Through u3 and the key load reference voltage u 3，ref After subtraction, it is obtained by PI controller, which is limited between 0 and 90°; Step 2: In the non-critical load voltage control, the secondary side voltage u2 is used as the controlled variable, and the phase shift angle ε 12 Through u2 and non-critical load reference voltage u 2，ref After subtraction, it is obtained by PI controller, which is limited between 0 and 90°; Step 3: In the energy storage battery control, when the energy storage unit starts working, u C4 The duty cycle D of the buck-boost converter is obtained by inputting the PI controller, and its value range is between 0 and 1.

7. A three-port power spring fluctuation suppression method according to claim 6, characterized in that: M 12 M is the voltage conversion ratio between the primary side and the secondary side 12 =u2 / nu1,M 13 is the voltage conversion ratio M between the primary side and the tertiary side 13 =u3 / nu1; The phase shift is required to meet the conditions for zero voltage switching: The first switch tube S1, the second switch tube S2, the third switch tube S3, the fourth switch tube S4, the fifth switch tube S5, the sixth switch tube S6, the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9, the tenth switch tube S 10 , Eleventh switch tube S 11 , the twelfth switch tube S 12 , Thirteenth switch tube S 13 , the fourteenth switch tube S 14 , the fifteenth switch tube S 15 and the sixteenth switch tube S 16 Both can achieve zero voltage turn-on.

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