Control method of multi-port photovoltaic and energy storage combined power generation system based on duty cycle

Abstract

The present invention discloses a control method for a multi-port photovoltaic-storage combined power generation system based on duty cycle. First, a mathematical model of high-voltage port output power based on duty cycle is established, and then a reference voltage vector on the AC side of the photovoltaic-storage combined power generation system is obtained. The sectors are divided according to the phase angle of the reference voltage vector to directly determine three duty cycles. The remaining three duty cycles are obtained by solving a set of three-variable linear equations related to the reference voltage vector and the reference high-voltage port power, wherein the reference high-voltage port power is described by a power mathematical model based on duty cycle. Finally, the obtained six duty cycles are compared with the triangular carrier amplitude to generate six switching signals for driving a multi-port inverter, thereby controlling the opening and closing of the switch tubes of each phase bridge arm.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic and energy storage combined power generation, and more specifically, relates to a control method for a multi-port photovoltaic and energy storage combined power generation system based on direct duty cycle calculation. Background Art

[0002] Photovoltaic arrays are a type of distributed power source with flexible configuration and low cost, and have been widely used. However, affected by natural factors such as light and temperature, photovoltaic power generation has the disadvantages of strong randomness and high intermittency. Energy storage units are usually added to photovoltaic power generation systems to smooth power fluctuations. Using a single-stage multi-port inverter to integrate photovoltaic arrays and energy storage units will effectively reduce system costs and improve system energy conversion efficiency.

[0003] Due to the real-time change of photovoltaic voltage in the photovoltaic-storage combined power generation system, the DC port voltage of the multi-port inverter will no longer be balanced. This will cause the phase angle and amplitude of the basic voltage vector in the space vector to change, thereby increasing the harmonic distortion of the AC current, thereby seriously reducing the power quality of the system. In addition, the shared power path of the multi-port inverter will also lead to increased DC port coupling, making it difficult for traditional power control methods to simultaneously achieve DC port power management and reference voltage vector synthesis in the photovoltaic-storage combined power generation system.

[0004] Existing multi-port inverter power control methods usually adopt improved modulation strategies to control the DC port power by injecting appropriate zero-sequence components into the modulation signal or adjusting the redundant vector. However, when the DC port voltage is unbalanced, these methods require complex modulation and control processes, which increases the difficulty of controller design, increases the computational burden, and slows down the system's dynamic response speed, making it impossible to effectively achieve the synthesis of the reference voltage vector and the tracking of the DC port power. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a control method for a multi-port photovoltaic and energy storage combined power generation system based on duty cycle. By directly calculating the duty cycle, it is easy to simultaneously realize the synthesis of reference voltage and the tracking of DC port power, thereby obtaining a grid-side current with high power quality and flexible DC-side power distribution.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a control method for a multi-port photovoltaic energy storage combined power generation system based on duty cycle, characterized in that it comprises the following steps:

[0007] (1) Collect the three-phase current i on the grid side of the multi-port photovoltaic and energy storage combined power generation system x , high voltage port voltage v h , and the current i at the high voltage port h, x=a, b, c represents the three phases of the power grid;

[0008] (2) Obtain the reference voltage vector u on the AC side of the photovoltaic and energy storage combined power generation system gref ;

[0009] (2.1) Given the reference voltage frequency f that is expected to be obtained on the AC grid side of the photovoltaic and energy storage combined power generation system, g , amplitude V g ;

[0010] (2.2) Calculate the voltage u on the grid side of the photovoltaic and energy storage combined power generation system g , multi-port inverter side current i1;

[0011]

[0012] Among them, V out is the output voltage of the multi-port inverter, i g is the grid-side current, R1, L1, and C are the resistance, inductance, and capacitance of the filter respectively;

[0013] (2.3), given the AC voltage frequency f g , amplitude V g ; The inverter side current i1 and the grid side voltage u g Input to the cascade PI control system to obtain the reference voltage vector u gref

[0014] (3) According to the phase angle of the reference voltage vector Divide sectors and classify duty cycles;

[0015] (3.1) Select the six voltage vectors V in the three-level vector modulation m1 、V m2 、V m3 、V m4 、V m5 、V m6 As basic voltage vectors, six basic voltage vectors are calculated by the following formulas:

[0016]

[0017] Where α = e j2π / 3 , v h 、v l They are high voltage port voltage and low voltage port voltage respectively;

[0018] (3.2), according to the reference voltage phase angle Divided into the following six sectors:

[0019]

[0020] in, Represents the phase angle of the voltage vector;

[0021] (3.3) According to the corresponding relationship between different sectors and duty cycles, the duty cycles of three switch signals among the six switch signals corresponding to the first switch and the second switch of each bridge arm of the multi-port inverter are determined. The corresponding relationship between the sectors and the three duty cycles is as follows:

[0022]

[0023] (4) Construct a set of equations related to the reference voltage vector and the high-voltage port power;

[0024] (4.1) Perform matrix transformation on the reference voltage to obtain the complex expression of the reference voltage:

[0025]

[0026] u gref =u grefα +j*u grefβ

[0027] Among them, u grefα 、u grefβ They are the complex reference voltage vector u gref The real and imaginary parts, u ga 、u gb 、u gc Corresponding to the reference voltage vector u gref The three-phase voltage;

[0028] (4.2), establish the real part of the reference voltage vector u grefα , imaginary part of reference voltage vector u grefβ And the high voltage port power P h Related system of three linear equations:

[0029]

[0030] (5) Solve the three-variable linear equation group related to the reference voltage vector and the high-voltage port power;

[0031] Given the high voltage port output power P h ; The three duty cycles and high-voltage port output power P determined by duty cycle classification h , the real part of the reference voltage vector u grefα , imaginary part of reference voltage vector u grefβ , high voltage port voltage v h , low voltage port voltage v l Substituting into the equation group, solving the three-variable linear equation group can obtain the remaining three duty cycle values;

[0032] With reference vector u gref For example, in the first sector, d 2a d 1b d 1c The three duty cycle values ​​are known, and d can be obtained by solving the three-variable linear equation system 1a d 2b d 2c ;

[0033] (6) In one switching cycle, the six duty cycles d 1a d 2a d 1b d 2b d 1c d 2c The triangular carrier amplitude is compared to generate six switching signals G that drive the multi-port inverter. a1 , G a2 , G b1 , G b2 , G c1 , G c2 , and then use the driving signal G x1 Control switch tube S 1x , driving signal G x1 Complementary signal control switch Drive signal G x2 Control switch tube S 2x , driving signal G x2 Complementary signal control switch Among them, S 1x , S 2x , They correspond to the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube of each bridge arm respectively.

[0034] The object of the invention of the present invention is achieved in this way:

[0035] The present invention proposes a control method for a multi-port photovoltaic and energy storage combined power generation system based on duty cycle. First, a mathematical model of the high-voltage port output power based on the duty cycle is established, and then a reference voltage vector on the AC side of the photovoltaic and energy storage combined power generation system is obtained. The sectors are divided according to the phase angle of the reference voltage vector to directly determine three duty cycles. The remaining three duty cycles are obtained by solving a set of three-variable linear equations related to the reference voltage vector and the reference high-voltage port power, wherein the reference high-voltage port power is described by a power mathematical model based on the duty cycle. Finally, the six duty cycles obtained are compared with the triangular carrier amplitude to generate six switching signals for driving the multi-port inverter, thereby controlling the opening and closing of the switch tubes of each phase bridge arm.

[0036] At the same time, the multi-port photovoltaic storage combined power generation system control method based on duty cycle of the present invention also has the following beneficial effects:

[0037] (1) The present invention can be effectively applied to the scenario of photovoltaic and energy storage combined power generation under the condition of variable DC port voltage, and has good steady-state performance even under the condition of unbalanced DC link voltage;

[0038] (2) The present invention avoids the heavy computational burden and complex modulation process while also ensuring the dynamic response capability of the photovoltaic-storage combined power generation system to quickly restore to a stable operating state when subjected to unexpected disturbances;

[0039] (3) A control method for a multi-port photovoltaic and energy storage combined power generation system with direct duty cycle calculation of the present invention can realize flexible power distribution of the DC port while providing controllable and high-quality AC power to the AC side public power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the structural topology diagram of the multi-port photovoltaic and energy storage combined power generation system;

[0041] Figure 2 This is a control block diagram of a multi-port photovoltaic and energy storage combined power generation system based on duty cycle;

[0042] Figure 3 It is a schematic diagram of sector division of the spatial voltage vector diagram of a multi-port photovoltaic and energy storage combined power generation system;

[0043] Figure 4 It is a schematic diagram of the reference voltage vector synthesis waveform of the multi-port photovoltaic energy storage combined power generation system under different port voltages according to the present invention;

[0044] Figure 5 It is a schematic diagram of DC port power distribution waveforms of a multi-port photovoltaic and energy storage combined power generation system under balanced port voltage according to the present invention;

[0045] Figure 6 It is a schematic diagram of the DC port power distribution waveform of the multi-port photovoltaic and energy storage combined power generation system under unbalanced port voltage according to the present invention;

[0046] Figure 7 It is a schematic diagram of the test results of the output power boost and voltage reduction of the high-voltage port of the multi-port photovoltaic and energy storage combined power generation system under constant grid power according to the present invention;

[0047] Figure 8 It is a schematic diagram of the test results of power grid power boosting and voltage reduction of a multi-port photovoltaic and energy storage combined power generation system under a constant high-voltage port output power according to the present invention;

[0048] Fig. 9It is a comparison chart of the deadbeat control based on space vector modulation, the PI control based on space vector modulation, and the dynamic response time when the output power of the high-voltage port on the DC side changes, which is realized according to the present invention, of a multi-port photovoltaic and energy storage combined power generation system. DETAILED DESCRIPTION

[0049] The specific implementation of the present invention is described below in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0050] Example

[0051] Figure 1 It is a structural topology diagram of a specific implementation method of a multi-port photovoltaic and energy storage combined power generation system.

[0052] In this embodiment, if Figure 1 As shown, the multi-port photovoltaic storage combined power generation system includes: a first DC voltage source 1, a second DC voltage source 2, DC side capacitors C1, C23, a diode 4, an LC filter 5 and a multi-port inverter 6;

[0053] The multi-port inverter includes two independent DC voltage sources, two DC side capacitors and three bridge arms, wherein the two DC voltage sources are respectively denoted as the first voltage source v h , the second voltage source v l ; The two DC side capacitors are denoted as the first DC capacitor C1 and the second DC capacitor C2; the corresponding first DC capacitor voltage is v1, and the second DC capacitor voltage is v2; the three bridge arms are denoted as the first bridge arm, the second bridge arm, and the third bridge arm; each bridge arm includes four switch tubes and two diodes, and the output terminals of the two central switch tubes and the two diodes are connected to the neutral point of the DC link, wherein the first bridge arm includes the first switch tube S 1a , the second switch tube S 2a , the third switch tube With the fourth switch The second switch tube S 2a , the third switch tube is the central switch tube of the first bridge arm; the second bridge arm includes the fifth switch tube S 1b , the sixth switch tube S 2b , the seventh switch tube With the eighth switch The sixth switch tube S 2b , the seventh switch tube is the central switch tube of the second bridge arm; the third bridge arm includes the ninth switch tube S 1c , the tenth switch tube S 2c 、11th switch tube With the twelfth switch The tenth switch tube S 2c 、11th switch tube It is the central switch tube of the third bridge arm;

[0054] It should be noted that the first DC power supply and the second DC voltage source are used to provide DC power to the system. Figure 1 As shown, the multi-port inverter provides direct power flow from the DC side to the AC side, with the advantages of small size and low cost. The diode is used to prevent the reverse flow of energy in the circuit and protect other devices from damage. DC capacitors C1 and C2 are used to stabilize the DC side voltage and absorb high-frequency harmonics. For the first to third bridge arms, 1 indicates that the switch tube of the bridge arm is turned on, and 0 indicates that the switch tube of the bridge arm is turned off.

[0055] like Figure 2 As shown, the following is a detailed description of a multi-port photovoltaic storage combined power generation system control method for direct duty cycle calculation of the present invention, which specifically includes the following steps:

[0056] (1) Data collection;

[0057] Obtain the three-phase current i on the grid side of the multi-port photovoltaic and energy storage combined power generation system x , high voltage port voltage v h , and the current i at the high voltage port h , x=a, b, c represents the three phases of the power grid;

[0058] S2. Calculate the reference voltage vector u on the AC side of the combined energy generation system gref ;

[0059] S2.1, given the reference voltage frequency f expected to be obtained on the AC grid side of the photovoltaic and energy storage combined power generation system g , amplitude V g ;

[0060] S2.2. Calculate the voltage u on the grid side of the photovoltaic and energy storage combined power generation system g , multi-port inverter side current i1;

[0061]

[0062] Among them, V out is the output voltage of the multi-port inverter, i g is the grid-side current, R1, L1, and C are the resistance, inductance, and capacitance of the filter respectively;

[0063] S2.3, given AC voltage frequency f g , amplitude V g ; The inverter side current i1 and the grid side voltage u gInput to the cascade PI control system to obtain the reference voltage vector u gref

[0064] S3, according to the phase angle of the reference voltage vector Divide sectors and classify duty cycles;

[0065] S3.1. Select six voltage vectors V in three-level vector modulation m1 、V m2 、V m3 、V m4 、V m5 、V m6 As basic voltage vectors, six basic voltage vectors are calculated by the following formulas:

[0066]

[0067] Where α = e j2π / 3 , v h v l They are high voltage port voltage and low voltage port voltage respectively;

[0068] S3.2, according to the reference voltage phase angle Divided into the following six sectors:

[0069]

[0070] in, Represents the phase angle of the voltage vector;

[0071] S3.3. According to the corresponding relationship between different sectors and duty cycles, the duty cycles of three switch signals among the six switch signals corresponding to the first switch and the second switch of each bridge arm of the multi-port inverter are determined. The corresponding relationship between the sectors and the three duty cycles is as follows:

[0072]

[0073] In this embodiment, the sector division of the spatial voltage vector diagram of the multi-port photovoltaic energy storage combined power generation system is as follows: Figure 3 As shown, (a) to (c) are schematic diagrams of sector division when the first DC capacitor voltage is equal to the second DC capacitor voltage, the first DC capacitor voltage is less than the second DC capacitor voltage, and the first DC capacitor voltage is greater than the second DC capacitor voltage. When the first DC capacitor voltage is equal to the second DC capacitor voltage, the six sectors are evenly distributed; when the first DC capacitor voltage is less than the second DC capacitor voltage, the first, third, and fifth sectors will be wider than the second, fourth, and sixth sectors; when the first DC capacitor voltage is greater than the second DC capacitor voltage, the second, fourth, and sixth sectors will be wider than the first, third, and fifth sectors. By summarizing the switching states of the switch tubes in different sectors, it can be found that the switch tube S in the same sector1x S 2x There are only two switch state combinations. Taking the first bridge arm as an example, when the reference vector is located in the first sector, only the first switch tube S 1a Turn on the second switch tube S 2a Open, the first switch tube S 1a Turn off the second switch S 2a In the above two switching situations, the second switch tube S 2a Both remain in the on state, thereby determining the duty cycle d of the switching signal of the second switch tube 2a =1, and so on, the duty cycle values ​​determined in the other two bridge arms can be obtained.

[0074] S4, constructing a set of equations related to the reference voltage vector and the high voltage port power;

[0075] S4.1. Perform matrix transformation on the reference voltage to obtain the complex expression of the reference voltage:

[0076]

[0077] u gref =u grefα +j*u grefβ

[0078] Among them, u grefα 、u grefβ They are the reference voltage vector u gref The plural form of u ga 、u gb 、u gc Corresponding to the reference voltage vector u gref Phase voltage of three phases;

[0079] S4.2. Establish the real part of the reference voltage vector u grefα , imaginary part of reference voltage vector u grefβ And the high voltage port power P h The relevant system of equations:

[0080]

[0081] In this embodiment, the second formula of the equation group gives a high-voltage port output power model based on the duty cycle, and the high-voltage port power P in the photovoltaic storage combined power generation system is h , low voltage port power P l , and the grid side active power P ac The following relationship is satisfied:

[0082] P h +P l =P ac =3Vg I g

[0083] Among them, V g ,I g Represents the RMS value of the voltage and current on the grid side. Therefore, at P ac Keeping constant, by adjusting P h Flexible power distribution between DC ports can be achieved.

[0084] S5, solving a set of three-variable linear equations related to the reference voltage vector and the high-voltage port power;

[0085] The three duty cycles determined by duty cycle classification and the given high voltage port power P h , the real part of the reference voltage vector u grefα , imaginary part of reference voltage vector u grefβ , high voltage port voltage v h , low voltage port voltage v l Substituting into the equation system, only three duty cycle values ​​are unknown. Therefore, solving the three-variable linear equation system can obtain the remaining three duty cycle values;

[0086] With reference vector u gref For example, in the first sector, d 2a d 1b d 1c The three duty cycle values ​​are known, and d can be obtained by solving the three-variable linear equation system 1a d 2b d 2c ;

[0087] S6, controlling the shutdown of each switch tube through a switch signal;

[0088] In one switching cycle, the six duty cycles d 1a d 2a d 1b d 2b d 1c d 2c The triangular carrier amplitude is compared to generate six switching signals G that drive the multi-port inverter. a1 , G a2 , G b1 , G b2 , G c1 , G c2 , and then use the driving signal G x1 Control switch tube S 1x , driving signal G x1 Complementary signal control switch Drive signal G x2 Control switch tube S2x , driving signal G x2 Complementary signal control switch Among them, S 1x , S 2x , They correspond to the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube of each bridge arm respectively.

[0089] Figure 4 The figure shows the schematic diagram of the reference voltage vector synthesis waveform of the multi-port photovoltaic energy storage combined power generation system under different port voltages according to the present invention; (a) v2 = 200V (v1 = v2), (b) v2 = 240V (v1 < v2), (b) v2 = 160V (v1 > v2). From top to bottom are the waveforms of sector changes, grid side voltage, duty cycle d 1a d 2a Waveform, a phase voltage waveform. Wherein, H(i) represents the i-th sector, and H(i), i=Ⅰ,Ⅱ,Ⅲ,Ⅳ,V,Ⅵ respectively represent the first to sixth sectors. Figure 4 As shown in (a), the action time of each sector is equal. Figure 4 In (b), the action time of the first, third, and fifth sectors is longer than that of the second, fourth, and sixth sectors. Figure 4 In (c), the action time of the second, fourth, and sixth sectors is longer than that of the first, third, and fifth sectors, which proves that the experimental results of sector selection are consistent with the theoretical analysis of the aforementioned sector division. According to the grid-side voltage waveform and phase voltage waveform analysis, it can be obtained that no matter what port voltage condition is, a voltage with higher power quality can be output. Therefore, the proposed strategy is effective under different port voltage conditions, and the desired sector division and duty cycle classification can be performed.

[0090] Figure 5 , 6 They are schematic diagrams of DC port power distribution waveforms achieved by a multi-port photovoltaic and energy-storage combined power generation system under balanced port voltage and unbalanced port voltage according to the present invention. Figure 5 From left to right: (a) P h =1kW(P h =P ac ), (b) P h =0.8kW(P h <P ac ), (c)P h =1.2kW(P h >P ac ), from top to bottom are the grid side voltage u ga , grid side flow i ga , grid side active power P ac , grid side reactive power Qac , high voltage port output power P h , low voltage port output power P l , line voltage v ba The reference grid side active power value is set to 1kW. Figure 5 It can be concluded that under different power distribution conditions, the proposed control method can well track the grid-side voltage, current and line voltage, and realize the power distribution between DC ports under three different power demands. Figure 6 The power distribution results under unbalanced port voltage are shown in Figure 1. From left to right, (a) v2 = 240 V (v1 < v2), (b) v2 = 160 V (v1 > v2). The waveform distribution order from top to bottom is the same as Figure 5 This shows that the proposed power control method is also effective under the condition of unbalanced port voltage. Figure 5 , 6 The results show that the proposed power control method can provide output current with high power quality under various DC port voltage conditions, and under the conditions of different port voltages and power allocation requirements, the proposed power control method can achieve accurate tracking of the high-voltage port output power.

[0091] Figure 7 , 8 It is a schematic diagram of the dynamic performance test results of a multi-port photovoltaic energy storage combined power generation system under the conditions of variable high-voltage port output power and grid-side active power according to the present invention. Figure 7 The test results of the sudden increase and decrease of the output power of the high-voltage port are shown in Figure 1. The results are as follows: (a) P h From 0.6kW to 1.2kW, (b) P h The experiment reduced the power from 1.2kW to 0.6kW, simulating the disturbance caused by the change of PV port voltage under constant grid power. Figure 8 The test results of the sudden increase and decrease of active power on the grid side are shown in Figure 1. The results are as follows: (a) P ac From 0.6kW to 1.2kW, (b) P ac The test simulates the disturbance caused by the change of power demand of the power grid under the condition of constant photovoltaic voltage. The above dynamic test verifies that the control method of the multi-port photovoltaic storage combined power generation system with direct duty cycle calculation of the present invention has fast dynamic performance when facing the possible interference of the photovoltaic storage combined power generation system, and can also ensure the stable output of high-quality voltage and current when the disturbance occurs.

[0092] Fig. 9The active power of the multi-port photovoltaic and energy storage combined power generation system on the grid side remains unchanged P ac Under the condition of , the deadbeat control based on space vector modulation, the PI control based on space vector modulation and the proposed power control method output power P at the high voltage port of the DC side h Comparison of dynamic response time from 0.6kW to 1.2kW. It can be seen that the proposed control method shows less execution time and faster dynamic response than the PI control based on space vector modulation. In addition, it is also proved that the proposed control method can realize DC port power distribution without using an additional control loop, and obtains the same fast dynamic performance as the deadbeat control method that realizes DC port power distribution through an indirect feedback loop, which further proves that the control method can effectively simplify the control system. The above comparative analysis can verify the performance superiority of this method compared with the existing methods.

[0093] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A control method for a multi-port photovoltaic energy storage combined power generation system based on duty cycle, characterized in that: The following steps are involved: (1) Collect the three-phase current i on the grid side of the multi-port photovoltaic and energy storage combined power generation system x , high voltage port voltage v h , and the current i at the high voltage port h , x=a, b, c represents the three phases of the power grid; (2) Obtain the reference voltage vector u on the AC side of the photovoltaic and energy storage combined power generation system gref ; (2.1) Given the reference voltage frequency f that is expected to be obtained on the AC grid side of the photovoltaic and energy storage combined power generation system, g , amplitude V g ; (2.2) Calculate the voltage u on the grid side of the photovoltaic and energy storage combined power generation system g , multi-port inverter side current i1; Among them, V out is the output voltage of the multi-port inverter, i g is the grid-side current, R1, L1, and C are the resistance, inductance, and capacitance of the filter respectively; (2.3), given the AC voltage frequency f g , amplitude V g ; The inverter side current i1 and the grid side voltage u g Input to the cascade PI control system to obtain the reference voltage vector u gref (3) According to the phase angle of the reference voltage vector Divide sectors and classify duty cycles; (3.1) Select the six voltage vectors V in the three-level vector modulation m1 、V m2 、V m3 、V m4 、V m5 、V m6 As basic voltage vectors, six basic voltage vectors are calculated by the following formulas: Where α = e j2π / 3 , v h v l They are high voltage port voltage and low voltage port voltage respectively; (3.2), according to the reference voltage phase angle Divided into the following six sectors: in, Represents the phase angle of the voltage vector; (3.3) According to the corresponding relationship between different sectors and duty cycles, the duty cycles of three switch signals among the six switch signals corresponding to the first switch and the second switch of each bridge arm of the multi-port inverter are determined. The corresponding relationship between the sectors and the three duty cycles is as follows: (4) Construct a set of equations related to the reference voltage vector and the high-voltage port power; (4.1) Perform matrix transformation on the reference voltage to obtain the complex expression of the reference voltage: in gref =in grefα +j*u grefβ Among them, u grefα 、u grefβ They are the complex reference voltage vector u gref The real and imaginary parts, u ga 、u gb 、u gc Corresponding to the reference voltage vector u gref The three-phase voltage; (4.2), establish the real part of the reference voltage vector u grefα , imaginary part of reference voltage vector u grefβ And the high voltage port power P h Related system of three linear equations: (5) Solve the three-variable linear equation group related to the reference voltage vector and the high-voltage port power; Given the high voltage port power P h ; The three duty ratios determined by duty ratio classification, high voltage port power P h , the real part of the reference voltage vector u grefα , imaginary part of reference voltage vector u grefβ , high voltage port voltage v h , low voltage port voltage v l Substituting into the equation group, solving the three-variable linear equation group can obtain the remaining three duty cycle values; (6) In one switching cycle, the six duty cycles d 1a ,d 2a ,d 1b ,d 2b ,d 1c ,d 2c The six driving signals G for driving the multi-port inverter are compared with the triangular carrier amplitude respectively. a1 , G a2 , G b1 , G b2 , G c1 , G c2 , and then use the driving signal G x1 Control switch tube S 1x , driving signal G x1 Complementary signal control switch Drive signal G x2 Control switch tube S 2x , driving signal G x2 Complementary signal control switch Among them, S 1x , S 2x , They correspond to the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube of each bridge arm respectively.

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