Autonomous power ripple suppression method based on grid-connected multi-port converter

Abstract

The invention discloses an autonomous power ripple suppression method based on a grid-connected multi-port converter, and the method comprises the steps: carrying out the negative-sequence current elimination at an AC port, carrying out the power ripple suppression at a DC port, automatically transferring a differential power ripple to a ripple port, and eliminating the dependence on the prior knowledge of the ripple; in addition, even under the unbalanced power grid working condition, balanced three-phase power grid current and ripple-free direct current output voltage can be obtained at the same time, and an additional power ripple controller does not need to be designed.

Description

Technical Field

[0001] The present invention belongs to the technical field of grid-connected control, and more particularly, relates to an autonomous power ripple suppression method based on a grid-connected multi-port converter. Background Art

[0002] With the deepening implementation of the global energy transition strategy and the rapid development of a low-carbon economy, renewable energy power generation systems are becoming an increasingly important component of the power system. In this context, grid-connected converters, as key interface devices connecting renewable energy to the power grid, have a direct impact on the stable operation and grid connection quality of the entire new energy system.

[0003] Under balanced grid voltage conditions, grid-connected converters are typically able to inject balanced current into the grid and maintain stable DC-side voltage. However, in practical power systems, grid voltage imbalance is common due to factors such as single-phase high-power loads, asymmetrical distribution line impedance, and various grid faults. This poses significant challenges to the control and operation of grid-connected converters. First, the interaction between the grid's negative-sequence voltage component and positive-sequence current component generates a dual-frequency oscillating power component. This power ripple is directly transmitted to the DC side, causing periodic fluctuations in the DC output voltage. Second, the injection of negative-sequence current into the grid generates asymmetric three-phase currents, which not only increases system line losses but also reduces the converter's effective power transfer capability. More seriously, the current in some phases may exceed the device rating, triggering local overheating and overcurrent protection, thereby affecting system reliability and service life.

[0004] To address the control challenges of grid-connected converters under unbalanced grid conditions, scholars at home and abroad have proposed various control schemes, primarily three types: constant active power control, balanced current control, and a compromise between the two. However, each of these schemes has limitations: constant active power control prioritizes maintaining DC voltage stability, often at the expense of grid current quality, resulting in significant negative-sequence current; balanced current control prioritizes ensuring a balanced sinusoidal current injected into the grid, but this can transfer power ripple to the DC side, causing DC voltage fluctuations; and compromise schemes attempt to strike a balance between the two, but are essentially a compromise, unable to simultaneously eliminate negative-sequence current and suppress power ripple.

[0005] In order to simultaneously achieve negative sequence current elimination and power ripple suppression, active power decoupling technology is another solution to improve the control performance of grid-connected converters. This technology actively buffers power ripple by introducing an additional power decoupling circuit (usually containing energy storage elements such as capacitors or inductors, and corresponding switching devices). However, this solution leads to additional costs and requires the design of additional resonant controllers or repetitive controllers to accurately control the power conversion in the decoupling circuit. In addition, there are also studies that use the inherent characteristics of specific topologies to achieve power decoupling, such as using a five-level flying capacitor converter. Although this type of solution does not require the addition of an independent decoupling circuit, its control strategy still requires the design of a dedicated power ripple control loop, and the control performance is highly dependent on prior knowledge of the power ripple. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide an autonomous power ripple suppression method based on a grid-connected multi-port converter. The method does not rely on prior knowledge of ripple and does not require the design of an additional power ripple controller. It can achieve effective power ripple suppression while eliminating negative sequence current, ensuring stable operation of the grid-connected system under unbalanced working conditions.

[0007] To achieve the above-mentioned object of the invention, the present invention provides an autonomous power ripple suppression method based on a grid-connected multi-port converter, characterized by comprising the following steps:

[0008] (1) Data collection;

[0009] Collect the three-phase voltage e on the AC side of the grid-connected multi-port converter x and three-phase current i x , x represents the phase, that is, x = a, b, c;

[0010] Collect the DC port voltage V of the grid-connected multi-port converter D and ripple port voltage V R ;

[0011] The output of the DC port voltage control loop of the grid-connected multi-port converter is extracted as the reference active power P * ; Extract the output of the ripple port voltage control loop of the grid-connected multi-port converter as the feedback control quantity Δk of the correction ratio k;

[0012] (2) Eliminate negative sequence current at the AC port of the grid-connected multi-port converter;

[0013] (2.1), the collected three-phase voltage e x and three-phase current i x Through the abc-αβ coordinate transformation unit, the grid voltage e in the stationary coordinate system is obtained αβ and grid current i αβ ;

[0014] (2.2) Use complex coefficient filter to extract grid voltage e αβ The positive sequence component and The grid voltage e αβ The component e in the stationary coordinate system α With e β Positive sequence components and Subtract and get the negative sequence component of the grid voltage and Using complex coefficient filter to extract grid current i αβ The positive sequence component and The component i of the grid current in the stationary coordinate system α with i β With positive sequence component and Subtract them respectively to get the negative sequence component of the grid current and

[0015] (2.3), according to the reference active power P * With positive sequence component and Calculation of the reference grid current for eliminating the negative sequence current component

[0016] (2.4), the reference grid current With the grid current i αβ The difference is then input into the proportional resonant controller for adjustment to achieve zero steady-state error tracking of the reference grid current.

[0017] (3) Decoupling modeling of grid-connected multi-port converters;

[0018] The grid-connected multi-port converter is decomposed into an upper-port converter and a lower-port converter using the decoupling modeling method, where the DC bus voltage of the upper-port converter is V D -V R Each bridge arm of the upper port converter has two switches, S x1 and S x3 ; The DC bus voltage of the lower port converter is V R Each bridge arm has two switches, namely S x2 and S x4 ;;

[0019] (4) Suppressing power ripple at the DC port of the grid-connected multi-port converter;

[0020] (4.1), the grid voltage e αβThe output voltage vector reference v is obtained by subtracting the output of the PR controller * ;

[0021] (4.2) Determine the adjustment ratio k, and adjust the active power P output by the DC port of the grid-connected multi-port converter by adjusting the ratio k. D , so that it tracks the reference active power P * ;

[0022] (4.3) According to the feedback control amount Δk, the adjustment ratio k is modified: k * =k+Δk,k * Indicates the adjusted ratio after correction;

[0023] (4.4), according to the modified adjustment ratio k * The voltage vector reference v * Decompose into and in, is the output voltage vector reference of the upper port converter, is the output voltage vector reference of the lower port converter;

[0024] (4.5) Synthesize the two output voltage vectors and The SVPWM modulation modules of the upper and lower port converters are input to generate the active switch S x1 、S x2 、S x3 、S x4 The driving signal G x1 , G x2 , G x3 , G x4 , thereby controlling the switching operation of each active switch and completing the control of the grid-connected multi-port converter.

[0025] The object of the invention of the present invention is achieved like this:

[0026] The present invention is based on an autonomous power ripple suppression method for a grid-connected multi-port converter. By performing negative-sequence current elimination at the AC port and implementing power ripple suppression at the DC port, the differential power ripple is automatically transferred to the ripple port, eliminating the reliance on prior knowledge of ripple. In addition, even under unbalanced grid conditions, balanced three-phase grid current and ripple-free DC output voltage can be obtained simultaneously without the need to design an additional power ripple controller.

[0027] At the same time, the autonomous power ripple suppression method based on the grid-connected multi-port converter of the present invention also has the following features:

[0028] Beneficial effects:

[0029] (1) The present invention realizes an autonomous power control strategy by adjusting the reference voltage vector of the converter, thereby reducing the complexity of the controller design;

[0030] (2) The present invention can effectively suppress the power ripple on the DC side. Even under severe grid voltage imbalance conditions, it can simultaneously obtain balanced three-phase grid current and stable DC output voltage, significantly improving the power quality and operational stability of the grid-connected system.

[0031] (3) The present invention performs negative sequence current elimination in the AC port and implements power ripple suppression in the DC port. The power ripple is automatically transferred to the ripple port in accordance with the power conservation principle, eliminating the design of the power ripple controller and the reliance on prior knowledge of ripple. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a model diagram of the grid-connected multi-port converter under the unbalanced grid voltage condition;

[0033] Figure 2 It is the circuit structure diagram of the grid-connected multi-port converter;

[0034] Figure 3 It is a schematic diagram of decoupling modeling of a grid-connected multi-port converter;

[0035] Figure 4 It is a control block diagram of the autonomous power ripple suppression method based on the grid-connected multi-port converter of the present invention;

[0036] Figure 5 The steady-state waveforms are shown when the single-phase grid voltage drops by 50%, with and without negative sequence current elimination and power ripple suppression applied to the grid-connected multi-port converter.

[0037] Figure 6 It is the dynamic waveform diagram of the grid-connected multi-port converter when a 50% drop in the single-phase grid voltage is suddenly applied;

[0038] Figure 7 The figure is a performance comparison diagram of power ripple suppression achieved by the traditional method and the present invention when the single-phase grid voltage drops by 80%. DETAILED DESCRIPTION

[0039] The following describes the specific embodiments of the present invention 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 detailed descriptions of known functions and designs may dilute the main content of the present invention, such descriptions will be omitted here.

[0040] Example

[0041] In this embodiment, the model of the grid-connected multi-port converter under the unbalanced grid voltage condition is as follows: Figure 1 As shown in the figure, unlike a traditional two-port converter, the grid-connected multi-port converter is a three-port network consisting of an AC port, a DC port, and a ripple port. By allowing the ripple port voltage to fluctuate, the power difference between the AC and DC ports can be transferred to the ripple port, thus ensuring the stability of the DC port voltage.

[0042] like Figure 2 As shown in Figure 1, the circuit structure of the grid-connected multi-port converter can be derived from the traditional midpoint-clamped three-level converter. From a structural perspective, this grid-connected multi-port converter can be considered an integration of two converters. Specifically, the interaction between the AC and DC ports is similar to that of a midpoint-clamped three-level converter, enabling power transmission and conversion between the two. The interaction between the AC and ripple ports is similar to that of an active power decoupling converter, effectively buffering and processing power ripple. Therefore, the multi-port converter employed can achieve both AC and DC power conversion while achieving power ripple buffering, avoiding the need for additional power decoupling circuitry.

[0043] Next, we introduce the specific structure of the grid-connected multi-port converter, as follows:

[0044] The grid-connected multi-port converter includes: a power conversion circuit, an AC port, a DC port and a ripple port;

[0045] The power conversion circuit is composed of a filter circuit and a three-phase bridge arm, wherein the filter circuit can be composed of a filter inductor L s Composition: The three-phase bridge arm includes the first bridge arm, the second bridge arm, and the third bridge arm, each of which contains two clamping diodes D x1 、D x2 and four active switches S x1 、S x2 、S x3 、S x4 ;

[0046] The AC port is connected to a three-phase AC source. Figure 2 e in a 、e b 、e c Indicates that the three output terminals of the three-phase AC source are connected to the three terminals a, b, and c of the AC side of the power conversion circuit respectively;

[0047] like Figure 2 As shown, the DC port voltage is V D , the port contains the DC bus capacitor C o and DC load R l , the DC bus capacitor C o and DC load Rl After being connected in parallel, its two ends are connected to the p and n terminals of the DC side of the power conversion circuit;

[0048] The ripple port voltage is V R , the port contains a decoupling capacitor C d , the decoupling capacitor C d The two ends of the circuit are connected to the o and n terminals on the DC side of the power conversion circuit.

[0049] Next, we will describe in detail the autonomous power ripple suppression method based on a grid-connected multi-port converter of the present invention. Figure 4 As shown, the following steps are included:

[0050] (1) Data collection and extraction;

[0051] Collect the three-phase voltage e on the AC side of the grid-connected multi-port converter x and three-phase current i x , x represents the phase, that is, x = a, b, c;

[0052] Collect the DC port voltage V of the grid-connected multi-port converter D and ripple port voltage V R ;

[0053] The output of the DC port voltage control loop of the grid-connected multi-port converter is extracted as the reference active power P * ; The output of the ripple port voltage control loop of the grid-connected multi-port converter is extracted as the feedback control quantity Δk of the correction ratio k.

[0054] (2) Eliminate negative sequence current at the AC port of the grid-connected multi-port converter;

[0055] (2.1), the collected three-phase voltage e x and three-phase current i x Through the abc-αβ coordinate transformation unit, the grid voltage e in the stationary coordinate system is obtained αβ and grid current i αβ ;

[0056] (2.2) Use complex coefficient filter to extract grid voltage e αβ The positive sequence component and The grid voltage e αβ The component e in the stationary coordinate system α With e β Positive sequence components and Subtract and get the negative sequence component of the grid voltage and Using complex coefficient filter to extract grid current i αβThe positive sequence component and The component i of the grid current in the stationary coordinate system α with i β With positive sequence component and Subtract them respectively to get the negative sequence component of the grid current and

[0057] In this embodiment, the complex coefficient filter transfer function is:

[0058]

[0059] Among them, ω0 is the grid angular frequency, ω c is the cutoff angular frequency, s represents the S domain;

[0060] (2.3), according to the reference active power P * With positive sequence component and Calculation of the reference grid current for eliminating the negative sequence current component

[0061] In this embodiment, the reference grid current The calculation method is:

[0062] Step 1: Calculate the active power and reactive power under unbalanced grid conditions;

[0063]

[0064] Among them, P0 and Q0 represent the active power P in and reactive power Q in The DC component of P r and Q r Represents P in and Q in The second-order AC component of

[0065] Step 2: To obtain a high power factor, ensure that the active power DC component P0 tracks the reference value P * , the reactive power DC component Q0 tracks the reference value 0. At the same time, in order to obtain a balanced three-phase grid current, the negative sequence component of the grid current should be eliminated and the control target is set:

[0066]

[0067] Step 3: Combine the power component calculation expression in step 1 with the control target in step 2 to calculate the reference grid current

[0068]

[0069] (2.4), the reference grid current With the grid current i αβ The difference is then input into the proportional-resonant (PR) controller for adjustment to achieve zero steady-state error tracking of the reference grid current.

[0070] In this embodiment, when the proportional resonant controller achieves zero steady-state error tracking of the reference grid current, negative sequence current elimination is successfully performed. At this time, the active power P of the AC port is in It is described as: P in =P * +P r , where active power ripple P r It is generated by the interaction between the negative sequence component of the grid voltage and the positive sequence component of the grid current and should be buffered by the ripple port.

[0071] (3) Decoupling modeling of grid-connected multi-port converters;

[0072] The grid-connected multi-port converter is decomposed into an upper-port converter and a lower-port converter using the decoupling modeling method, where the DC bus voltage of the upper-port converter is V D -V R Each bridge arm of the upper port converter has two switches, S x1 and S x3 ; The DC bus voltage of the lower port converter is V R Each bridge arm has two switches, namely S x2 and S x4 ;

[0073] like Figure 3 As shown in FIG, in this embodiment, a decoupling modeling method is used to simplify the modulator design and improve the flexibility of power ripple suppression. Through decoupling modeling, the multi-port converter is decomposed into two two-port converters: the DC bus voltage is V D -V R The upper port converter and DC bus voltage is V R The lower port converter of x1 and S x3 are the two complementary switches of the upper port converter, S x2 and S x4 These are the two complementary switches of the lower port converter. This decomposition method brings significant advantages. On the one hand, the asymmetrically distributed space vector can be decomposed into two uniformly distributed space vectors, simplifying the modulator design. On the other hand, the reference voltage vector is decomposed into the reference voltage vector of the upper port converter. and the reference voltage vector of the upper port converter Improved the flexibility of power ripple suppression.

[0074] (4) Suppressing power ripple at the DC port of the grid-connected multi-port converter;

[0075] (4.1), the grid voltage e αβ The output voltage vector reference v is obtained by subtracting the output of the PR controller * ;

[0076] (4.2) Determine the adjustment ratio k, and adjust the active power P output by the DC port of the grid-connected multi-port converter by adjusting the ratio k. D , so that it tracks the reference active power P * , when the reference active power P * After being effectively tracked, according to the power conservation principle, the power ripple P generated on the AC side r It will automatically transfer to the ripple port;

[0077] In this embodiment, the allocation ratio k is determined as follows:

[0078] Step 1: Considering the power balance between the input and output of the grid-connected multi-port converter, calculate the active power output of the grid-connected multi-port converter:

[0079]

[0080] Among them, P U and P L are the active power output by the upper port converter and the lower port converter, is the grid current vector i αβ conjugation of;

[0081] Step 2: Assuming that the three-phase grid current is constant in each control cycle, calculate the active power P output by the DC port of the grid-connected multi-port converter D :

[0082]

[0083] Among them, V D is the DC port voltage, i x is the grid current per phase, d x1 is the active switch S x1 Duty cycle;

[0084] Step 3: Calculate the active power P output by the upper port converter U :

[0085]

[0086] Step 4: Based on the results of steps 1 and 3, calculate the active power P D It is expressed as follows:

[0087]

[0088] Step 5: Calculate the distribution ratio k:

[0089]

[0090] (4.3) According to the feedback control amount Δk, the adjustment ratio k is modified: k * =k+Δk,k * Indicates the adjusted ratio after correction;

[0091] (4.4), according to the modified adjustment ratio k * The voltage vector reference v * Decompose into and in, is the output voltage vector reference of the upper port converter, is the output voltage vector reference of the lower port converter;

[0092] (4.5) Synthesize the two output voltage vectors and The SVPWM modulation modules of the upper and lower port converters are input to generate the active switch S x1 、S x2 、S x3 、S x4 The driving signal G x1 , G x2 , G x3 , G x4 , thereby controlling the switching operation of each active switch and completing the control of the grid-connected multi-port converter.

[0093] Example verification

[0094] The following describes the second embodiment with reference to examples. Figure 5-Figure 7 As shown in the figure. The experiment sets the grid voltage to be 55V and the grid frequency to be stable at 50Hz. In terms of load configuration, the DC load R l A linear load with a resistance of 80Ω is selected. In terms of circuit component parameter selection, the decoupling capacitor C d The capacitance is 120μF, the DC port capacitor C o The capacitance is 150μF, the filter inductor L s The inductance is 5mH. In addition, the control frequency is set to 10kHz. In order to simplify the experimental analysis, the ripple port voltage reference Set as DC port voltage reference half.

[0095] Figure 5 The steady-state waveforms of the grid-connected multi-port converter with and without negative sequence current elimination and power ripple suppression are shown when the single-phase grid voltage drops by 50%. From top to bottom, they are: DC port voltage V D , ripple port voltage V R , power ripple P r , ripple port active power P R , and the three-phase grid current i abc .exist Figure 5 In (a), the grid-connected multi-port converter is not applying either negative-sequence current cancellation or power ripple suppression. The waveform clearly shows severe distortion of the three-phase grid current, with the presence of numerous harmonics. This is due to the negative-sequence current, which creates an imbalance in the three-phase currents and severely impacts the grid's power quality. Figure 5 (b) shows the case where only negative sequence current elimination is applied but power ripple suppression is not applied. At this time, the three-phase grid current is balanced, which shows that the negative sequence current elimination measures have effectively played a role and improved the current quality on the grid side. However, there is still significant ripple in the DC port voltage, and its peak-to-peak value is large, which shows that only eliminating the negative sequence current cannot solve the impact of power ripple on the DC port voltage, and the stability of the DC side is still threatened. In contrast, Figure 5 In (c), negative-sequence current elimination and power ripple suppression are applied simultaneously. In this case, the three-phase grid current remains balanced, and the ripple of the DC port voltage is effectively suppressed, with fluctuations significantly reduced. This clearly demonstrates the effectiveness of the control strategy proposed in the present invention. By simultaneously implementing negative-sequence current elimination and power ripple suppression, it is possible to ensure the stable operation of the grid-connected multi-port converter under the condition of a single-phase grid voltage drop, provide high-quality power output to the grid, and ensure the stable operation of the DC-side equipment.

[0096] Figure 6 It shows the dynamic waveform of the grid-connected multi-port converter when the single-phase grid voltage suddenly drops by 50%. From top to bottom, they are: reactive power Q in , reference active power P * , active power P in , DC port active power P D , ripple port active power P R , and the three-phase grid current i abc. It can be seen that when an unbalanced grid voltage condition occurs suddenly, a significant phenomenon is that reactive power ripple is quickly injected into the AC port. This mechanism plays a key role in maintaining the balance of the three-phase grid current. By injecting reactive power ripple, the current imbalance caused by voltage drop is effectively compensated, ensuring that the three-phase current can remain balanced under abnormal conditions. In addition, it can be observed that the active power of the AC port and the DC port can track the reference active power. Therefore, the power ripple will be automatically transferred to the ripple port in accordance with the power conservation principle without the need for an additional ripple controller.

[0097] Figure 7 This is a performance comparison chart of the power ripple suppression achieved by the conventional method and the present invention when the single-phase grid voltage drops by 80% in the second embodiment of the present invention. From top to bottom: DC port voltage V D , ripple port voltage V R , three-phase grid current i abc , power ripple P r , ripple port active power P R , and the power ripple tracking error P rr =P R -P r . Figure 7 (a) shows the control performance of a traditional PR controller. During a severe grid voltage sag, the traditional PR controller-based solution exhibits significant shortcomings. Its root mean square (RMS) tracking error reaches 56.54W, while the peak-to-peak DC port voltage reaches 11.70V. This indicates that the solution has a significant deviation in tracking the reference value and cannot accurately control power output. Figure 7 (b) Demonstrates the control performance of the present invention. Because the present invention overcomes the limitations of traditional methods that rely on prior knowledge of power ripple, eliminating the need for a complex and precisely tuned ripple controller, the present solution demonstrates excellent performance under the same grid voltage drop conditions. Its RMS tracking error is only 28.82W, effectively improving power tracking accuracy. The peak-to-peak DC port voltage is even lower, at only 6.32V, ensuring stable DC port voltage output.

[0098] Although the above describes the illustrative specific embodiments of the present invention to facilitate understanding of the present invention by those skilled in the art, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concepts of the present invention are protected.

Claims

1. An autonomous power ripple suppression method based on a grid-connected multi-port converter, characterized in that: The following steps are involved: (1) Data collection; Collect the three-phase voltage e on the AC side of the grid-connected multi-port converter x and three-phase current i x , x represents the phase, i.e. x = a, b, c; Collect the DC port voltage V of the grid-connected multi-port converter D and ripple port voltage V R ; The output of the DC port voltage control loop of the grid-connected multi-port converter is extracted as the reference active power P * ; The output of the ripple port voltage control loop of the grid-connected multi-port converter is extracted as the feedback control quantity Δk for the correction ratio k; (2) Eliminate negative sequence current at the AC port of the grid-connected multi-port converter; (2.1), the collected three-phase voltage e x and three-phase current i x Through the abc-αβ coordinate transformation unit, the grid voltage e in the stationary coordinate system is obtained αβ and grid current i αβ ; ( 2.2) Use complex coefficient filter to extract grid voltage e αβ The positive sequence component and The grid voltage e αβ The component e in the stationary coordinate system α With e β Positive sequence components and Subtract and get the negative sequence component of the grid voltage and Using complex coefficient filter to extract grid current i αβ The positive sequence component and The component i of the grid current in the stationary coordinate system α with i β With positive sequence component and Subtract them respectively to get the negative sequence component of the grid current and (2.3), according to the reference active power P * With positive sequence component and Calculation of the reference grid current for eliminating the negative sequence current component (2.4), the reference grid current With the grid current i αβ The difference is then input into the proportional resonant controller for adjustment to achieve zero steady-state error tracking of the reference grid current. (3) Decoupling modeling of grid-connected multi-port converters; The grid-connected multi-port converter is decomposed into an upper-port converter and a lower-port converter using the decoupling modeling method, where the DC bus voltage of the upper-port converter is V D -V R Each bridge arm of the upper port converter has two switches, S x1 and S x3 ; The DC bus voltage of the lower port converter is V R Each bridge arm has two switches, namely S x2 and S x4 ; (4) Suppressing power ripple at the DC port of the grid-connected multi-port converter; (4.1), the grid voltage e αβ The output voltage vector reference v is obtained by subtracting the output of the PR controller * ; (4.2) Determine the adjustment ratio k, and adjust the active power P output by the DC port of the grid-connected multi-port converter by adjusting the ratio k. D , so that it tracks the reference active power P * ; (4.3) According to the feedback control amount Δk, the adjustment ratio k is modified: k * =k+Δk,k * Indicates the adjusted ratio after correction; (4.4), according to the modified adjustment ratio k * The voltage vector reference v * Decompose into and in, is the output voltage vector reference of the upper port converter, is the output voltage vector reference of the lower port converter; (4.5) Synthesize the two output voltage vectors and The SVPWM modulation modules of the upper and lower port converters are input to generate the active switch S x1 、S x2 、S x3 、S x4 The driving signal G x1 , G x2 , G x3 , G x4 , thereby controlling the switching operation of each active switch and completing the control of the grid-connected multi-port converter.

2. The autonomous power ripple suppression method based on a grid-connected multi-port converter according to claim 1, characterized in that: The complex coefficient filter transfer function is: Among them, ω0 is the grid angular frequency, ω c is the cutoff angular frequency, and s represents the S domain.

3. The autonomous power ripple suppression method based on a grid-connected multi-port converter according to claim 1, characterized in that: The reference grid current The calculation method is: Step 1: Calculate the active power and reactive power under unbalanced grid conditions; Among them, P0 and Q0 represent the active power P in and reactive power Q in The DC component of P r and Q r Represents P in and Q in The second-order AC component of are the positive sequence components of the grid voltage and grid current in the stationary coordinate system respectively; are the negative sequence components of the grid voltage and grid current in the stationary coordinate system respectively; Step 2: Set control objectives: Step 3: Calculate the reference grid current based on the control target 4. The autonomous power ripple suppression method based on a grid-connected multi-port converter according to claim 1, characterized in that: The method for determining the allocation ratio k is: Step 1: Considering the power balance between the input and output of the grid-connected multi-port converter, calculate the active power output of the grid-connected multi-port converter: Among them, P U and P L are the active power output by the upper port converter and the lower port converter, is the grid current vector i αβ conjugation of; Step 2: Assuming that the three-phase grid current is constant in each control cycle, calculate the active power P output by the DC port of the grid-connected multi-port converter D : Among them, V D is the DC port voltage, i x is the grid current per phase, d x1 is the active switch S x1 Duty cycle; Step 3: Calculate the active power P output by the upper port converter U : Step 4: Based on the results of steps 1 and 3, calculate the active power P D It is expressed as follows: Step 5: Calculate the allocation ratio k:

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