A model predictive decoupling control method and system for a TAB-PFC

Abstract

The present disclosure provides a model prediction decoupling control method and system for TAB-PFC, which comprises: periodically sampling the output voltage and inductance current of the ring bipolar DC power distribution network system at the current time, and calculating the target output voltage; according to the obtained sampling values of the output voltage and inductance current, using the pre-constructed output voltage prediction model of the ring bipolar DC power distribution network system, the voltage prediction values under four different switch combinations of the TAB-PFC simplified circuit are obtained; according to the voltage prediction values under different switch combinations, using the pre-constructed cost function, the cost values corresponding to different switch combinations are obtained; wherein the cost function is constructed based on the voltage prediction value and the target output voltage; selecting the switch combination with the minimum cost value as the control signal of each switch tube in the next period, and through the periodic execution of the above process, the model prediction decoupling control of TAB-PFC is realized.

Description

Technical Field

[0001] This disclosure belongs to the field of power electronic device control technology for DC distribution network power flow control, and particularly relates to a model prediction decoupling control method and system of TAB-PFC. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] In a ring-shaped DC distribution network, there may be multiple transmission lines between distributed generation sources. The power flow on each line depends only on the voltage difference between its two ends and the line resistance. If the voltages of two distributed generation sources are equal, then there is no power flow between them. Therefore, relying solely on the power coordination between the distributed generation sources themselves is insufficient to achieve effective power flow control of the system and may also cause unnecessary line losses, jeopardizing the safe and stable operation of the system.

[0004] Compared to unipolar DC distribution networks, bipolar DC distribution networks have multi-voltage level interfaces, which can meet diverse load demands and improve power transmission efficiency. Simultaneously, bipolar DC distribution networks have reliable grounding; when one pole fails, the other pole can continue operating, ensuring continuous power supply and achieving high power quality. However, due to the presence of a neutral wire in its structure, coupling exists between the positive and negative poles of a bipolar DC distribution network. When the loads or other electrical parameters of the positive and negative poles are different, the system becomes unbalanced. In this case, continuous unbalanced current will flow into the neutral wire, causing power loss due to the neutral wire's line resistance.

[0005] like Figure 1 As shown, the Three Active Bridge Series-Parallel DC Power Flow Controller (TAB-PFC) is an effective solution to the above two problems. It consists of one TAB converter and two full-bridge converters. The input of the TAB-PFC is connected in parallel with the DC bus of the bipolar DC grid, and the output is connected in series with the positive and negative DC buses, respectively, which is equivalent to connecting two controllable voltage sources in series in the transmission line. By controlling the output voltage of the TAB-PFC, the transmission power of the positive and negative lines is controlled, ensuring that the power flow on the line follows the set value and is unaffected by load or voltage imbalance at the receiving end.

[0006] The inventors discovered that in the control of TAB-PFC, decoupling the TAB and using constant voltage control to keep its output voltage constant results in coupling between the positive and negative control loops of the two full-bridge converters, leading to large line power flow and current ripple, and poor dynamic performance. Existing solutions introduce a decoupling matrix into the control loop; however, since solving the ideal decoupling matrix is ​​extremely complex, only an approximate solution can be obtained, achieving approximate decoupling of the positive and negative control loops, thus offering limited improvement in dynamic performance. Furthermore, existing solutions assume V during approximate decoupling.dc1 =V dc2 Therefore, it is relatively simple to implement, but when V dc1 ≠V dc2 At that time, existing methods are difficult to implement. Summary of the Invention

[0007] To address the aforementioned issues, this disclosure provides a model predictive decoupling control method and system for TAB-PFC. The scheme employs a finite set model predictive control method, introducing a cost function that includes the output voltage to achieve complete decoupling of the positive and negative control loops. The implementation is simple and easy to implement; moreover, it eliminates the need for cascading multiple PI controllers, overcoming the bandwidth limitations of existing methods and significantly improving the system's response speed.

[0008] According to a first aspect of the embodiments of this disclosure, a model prediction decoupling control method for TAB-PFC is provided, comprising:

[0009] The output voltage and inductor current of the ring bipolar DC distribution network system at the current moment are sampled periodically, and the target output voltage is calculated. The ring bipolar DC distribution network system includes a TAB-PFC converter.

[0010] Based on the obtained output voltage and inductor current sampling values, the voltage prediction values ​​of the four half-bridges under different switching combinations in the TAB-PFC simplified circuit are obtained using the pre-constructed output voltage prediction model of the ring bipolar DC distribution network system.

[0011] Based on the voltage prediction values ​​under different switch combinations, the cost value corresponding to different switch combinations is obtained using a pre-constructed cost function; wherein, the cost function is constructed based on the voltage prediction values ​​and the target output voltage.

[0012] The switch combination with the lowest cost is selected as the control signal for each switch in the next cycle. By periodically executing the above process, model predictive decoupling control of TAB-PFC is achieved.

[0013] Furthermore, the output voltage prediction model for the ring bipolar DC distribution network system is specifically represented as follows:

[0014]

[0015]

[0016] Among them, v k1 v k2 V1 and V2 are the line receiving-end voltages, and a, b, c, d, and e are constants. T is the output voltage of the TAB-PFC. S S is the discrete time step. a Sb S c S d These represent the switching states of the four half-bridges, C1 and C2 are output capacitors, L1 and L2 are inductors, and V... dc1 V dc2 It is a constant voltage.

[0017] Furthermore, the cost function is specifically expressed as follows:

[0018]

[0019] Among them, v k1 (k+1), v k2 (k+1) represents the predicted voltage of the TAB-PFC output at time k+1. The target output voltage.

[0020] Furthermore, the calculation of the target output voltage specifically involves: based on the relationship between the positive and negative pole transmission power and the line current of the ring bipolar DC distribution network system, and based on the given value of the positive and negative pole line transmission power, calculating the target output voltage of TAB-PFC.

[0021] Furthermore, the different combinations of switches in the four half-bridges are specifically defined as follows: the switches of the four half-bridges are defined as {S}. a S b S c S d}, where {S a S b S c S d The switch state combination of} consists of {0000}, {0001}, {0010}, {0011}, {0100}, {0101}, {0110}, {0111}, {1000}, {1001}, {1010}, {1011}, {1100}, {1101}, {1110}, {1111}.

[0022] According to a second aspect of the present disclosure, a model prediction decoupling control system for TAB-PFC is provided, comprising:

[0023] The data acquisition unit is used to periodically sample the output voltage and inductor current of the ring bipolar DC distribution network system at the current moment and calculate the target output voltage. The ring bipolar DC distribution network system includes a TAB-PFC converter.

[0024] The voltage prediction value acquisition unit is used to obtain the voltage prediction values ​​of the four half-bridges under different switching combinations in the TAB-PFC simplified circuit based on the obtained output voltage and inductor current sampling values ​​and using the pre-built output voltage prediction model of the ring bipolar DC distribution network system.

[0025] The cost value acquisition unit is used to obtain the cost value corresponding to different switching combinations based on the voltage prediction value under different switching combinations and using a pre-constructed cost function; wherein, the cost function is constructed based on the voltage prediction value and the target output voltage.

[0026] The decoupling control unit is used to select the switch combination with the lowest cost as the control signal for each switch in the next cycle. By periodically executing the above process, model predictive decoupling control of TAB-PFC is realized.

[0027] According to a third aspect of the present disclosure, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and running on the memory, wherein the processor executes the program to implement the TAB-PFC model prediction decoupling control method described above.

[0028] According to a fourth aspect of the present disclosure, a non-transitory computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the TAB-PFC model prediction decoupling control method described above.

[0029] Compared with the prior art, the beneficial effects of this disclosure are:

[0030] (1) This disclosure provides a model prediction decoupling control method and system for TAB-PFC. The scheme adopts the finite set model prediction control method, introduces a cost function including the output voltage, realizes the complete decoupling of the positive and negative control loops, and the implementation scheme is simple and easy to implement. Moreover, it does not require the cascading of multiple PI controllers, breaks through the bandwidth limitation of the existing method, and greatly improves the response speed of the system.

[0031] (2) The solution described in this disclosure can effectively reduce line current and power flow ripple, and improve the dynamic performance of the system.

[0032] Advantages of this disclosure in additional aspects will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0033] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure.

[0034] Figure 1 This is a schematic diagram of the TAB-PFC topology described in the embodiments of this disclosure;

[0035] Figure 2 This is the equivalent circuit of the ring bipolar DC distribution network containing TAB-PFC described in the embodiments of this disclosure;

[0036] Figure 3 This is a simplified schematic diagram of a ring bipolar DC distribution network structure containing TAB-PFC as described in the embodiments of this disclosure;

[0037] Figure 4 This is a flowchart of a model prediction decoupling control method for TAB-PFC as described in an embodiment of this disclosure. Detailed Implementation

[0038] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this disclosure. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] Where there is no conflict, the embodiments and features described herein can be combined with each other.

[0042] Example 1:

[0043] The purpose of this embodiment is to provide a model prediction decoupling control method for TAB-PFC.

[0044] like Figure 4 As shown, a model prediction decoupling control method for TAB-PFC includes:

[0045] The output voltage and inductor current of the ring bipolar DC distribution network system at the current moment are sampled periodically, and the target output voltage is calculated. The ring bipolar DC distribution network system includes a TAB-PFC converter.

[0046] Based on the obtained output voltage and inductor current sampling values, the voltage prediction values ​​of the four half-bridges under different switching combinations in the TAB-PFC simplified circuit are obtained using the pre-constructed output voltage prediction model of the ring bipolar DC distribution network system.

[0047] Based on the voltage prediction values ​​under different switch combinations, the cost value corresponding to different switch combinations is obtained using a pre-constructed cost function; wherein, the cost function is constructed based on the voltage prediction values ​​and the target output voltage.

[0048] The switch combination with the lowest cost is selected as the control signal for each switch in the next cycle. By periodically executing the above process, model predictive decoupling control of TAB-PFC is achieved.

[0049] Furthermore, the output voltage prediction model for the ring bipolar DC distribution network system is specifically represented as follows:

[0050]

[0051]

[0052] Among them, v k1 v k2 V1 and V2 are the line receiving-end voltages, and a, b, c, d, and e are constants. T is the output voltage of the TAB-PFC. S S is the discrete time step. a S b S c S d These represent the switching states of the four half-bridges, C1 and C2 are output capacitors, L1 and L2 are inductors, and V... dc1 V dc2 It is a constant voltage.

[0053] Furthermore, the cost function is specifically expressed as follows:

[0054]

[0055] Among them, v k1 (k+1), v k2 (k+1) represents the predicted voltage of the TAB-PFC output at time k+1. The target output voltage.

[0056] Furthermore, the calculation of the target output voltage specifically involves: based on the relationship between the positive and negative pole transmission power and the line current of the ring bipolar DC distribution network system, and based on the given value of the positive and negative pole line transmission power, calculating the target output voltage of TAB-PFC.

[0057] Furthermore, the different combinations of switches in the four half-bridges are specifically defined as follows: the switches of the four half-bridges are defined as {S}. a S b S c S d}, where {S a S b S c S d The switch state combination of} consists of {0000}, {0001}, {0010}, {0011}, {0100}, {0101}, {0110}, {0111}, {1000}, {1001}, {1010}, {1011}, {1100}, {1101}, {1110}, {1111}.

[0058] Specifically, for ease of understanding, the following detailed description of the solution in this embodiment is provided in conjunction with the accompanying drawings:

[0059] To address the problems existing in the prior art, the solution described in this embodiment employs a finite set model predictive control method, introducing a cost function that includes the output voltage to achieve complete decoupling of the positive and negative control loops. The implementation steps are clear, straightforward, and easy to follow. Furthermore, it eliminates the need for cascading multiple PI controllers, overcoming the bandwidth limitations of existing methods and significantly improving the system's response speed. Specifically, a TAB-PFC model predictive decoupling control method includes:

[0060] (I) Model Building Phase

[0061] The equivalent circuit of a ring bipolar DC distribution network with a TAB-PFC converter is as follows: Figure 2 As shown, the relationship between the positive and negative power transmission and the line current is known to be:

[0062]

[0063]

[0064] i p =-av k1 -bv k2 +cV1+dV2+e (3)

[0065] i n =-bv k1 -av k2 +dV1+cV2+e (4)

[0066] Where P1 and P2 are the transmission powers of the positive and negative lines, respectively, and v1-v9 are... Figure 2 Line node voltage, v k1 v k2i is the output voltage of TAB-PFC p i n V1 and V2 are the currents on the positive and negative transmission lines, respectively, and the receiving-end voltages of the lines are V1 and V2. A, B, C, D, and E are constants, the expressions of which can be found in the literature "Unbalanced Power Flow Suppression of Ring Bipolar DC Distribution Network Based on Three-Active Bridge Series-Parallel DC Power Flow Controller" [J]. Journal of Electrical Engineering, He Dalu, Liao Jianquan, Wang Qianggang, which will not be repeated here. According to equations (1) and (2) and the given values ​​of the transmission power of the positive and negative lines. Calculate the target output voltage setpoint of TAB-PFC

[0067] The TAB section of the converter uses constant voltage control to ensure the output voltage V dc1 V dc2 Constant, therefore V dc1 V dc2 As a constant value, the simplified circuit of TAB-PFC is as follows: Figure 3 As shown. The characteristic equations for the output capacitors C1 and C2, and the inductors L1 and L2 are:

[0068]

[0069]

[0070]

[0071]

[0072] Discretizing equations (7) and (8) using the backward Euler method yields:

[0073]

[0074]

[0075] Among them, T S S is the discrete time step. a S b S c S d These represent the switching states of the four half-bridges. When the upper transistor of a half-bridge is turned on, S is defined. i =1 (i=a,b,c,d), when the lower transistor of the half-bridge is turned on, define S. i =0 (i=a,b,c,d). {S a S b S c S dThe switch state combinations of} can only be 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111.

[0076] Discretizing equations (5) and (6) using the forward Euler method yields:

[0077]

[0078]

[0079] Substituting equations (9) and (10) into equations (11) and (12) yields v k1 v k2 The prediction model is:

[0080]

[0081]

[0082] The substitution valence function is:

[0083]

[0084] (II) Predictive Control Stage

[0085] Step 1: Calculate the current output voltage v of the system. k1 v k2 Inductor current i L1 i L2 Sample the voltage and calculate the target output voltage.

[0086] Step 2: Transfer the v obtained in Step 1 k1 v k2 i L1 i L2 Substitute the sampled values ​​into formulas (13) and (14), and iterate through {S} a S b S c S d 16 switch combinations.

[0087] Step 3: Calculate the result v k1 (k+1) and v k2 Substitute (k+2) into the cost function to calculate the cost function value corresponding to each switch combination.

[0088] Step 4: Find the switch combination {S} that minimizes the cost function. a S b S c Sd This serves as the control signal for each switching transistor in the next cycle.

[0089] By repeating the above steps, the positive and negative control loops of the TAB-PFC converter in a ring bipolar DC distribution network under model predictive control can be completely decoupled.

[0090] Example 2:

[0091] The purpose of this embodiment is to provide a model prediction decoupling control system for TAB-PFC.

[0092] A model predictive decoupling control system for TAB-PFC includes:

[0093] The data acquisition unit is used to periodically sample the output voltage and inductor current of the ring bipolar DC distribution network system at the current moment and calculate the target output voltage. The ring bipolar DC distribution network system includes a TAB-PFC converter.

[0094] The voltage prediction value acquisition unit is used to obtain the voltage prediction values ​​of the four half-bridges under different switching combinations in the TAB-PFC simplified circuit based on the obtained output voltage and inductor current sampling values ​​and using the pre-built output voltage prediction model of the ring bipolar DC distribution network system.

[0095] The cost value acquisition unit is used to obtain the cost value corresponding to different switching combinations based on the voltage prediction value under different switching combinations and using a pre-constructed cost function; wherein, the cost function is constructed based on the voltage prediction value and the target output voltage.

[0096] The decoupling control unit is used to select the switch combination with the lowest cost as the control signal for each switch in the next cycle. By periodically executing the above process, model predictive decoupling control of TAB-PFC is realized.

[0097] Furthermore, the system described in this embodiment corresponds to the method described in Embodiment 1, and its technical details have been described in detail in Embodiment 1, so they will not be repeated here.

[0098] In further embodiments, the following is also provided:

[0099] An electronic device includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor. When executed by the processor, the computer instructions perform the method described in Embodiment 1. For brevity, further details are omitted here.

[0100] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0101] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.

[0102] A computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the method described in Embodiment 1.

[0103] The method in Embodiment 1 can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor. The software modules can reside in readily available storage media in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory; the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method. To avoid repetition, a detailed description is not provided here.

[0104] Those skilled in the art will recognize that the units, i.e., algorithm steps, of the various examples described in connection with this embodiment can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this disclosure.

[0105] The TAB-PFC model prediction decoupling control method and system provided in the above embodiments can be implemented and has broad application prospects.

[0106] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A model prediction decoupling control method for TAB-PFC, characterized in that, include: The output voltage and inductor current of the ring bipolar DC distribution network system at the current moment are sampled periodically, and the target output voltage is calculated. The ring bipolar DC distribution network system includes a TAB-PFC converter. Based on the obtained output voltage and inductor current sampling values, the voltage prediction values ​​of the four half-bridges under different switching combinations in the TAB-PFC simplified circuit are obtained using the pre-constructed output voltage prediction model of the ring bipolar DC distribution network system. The output voltage prediction model for the ring bipolar DC distribution network system is specifically represented as follows: in, v k1 , v k2 This refers to the output voltage of the TAB-PFC. V 1. V 2 represents the receiving-end voltage of the line. a , b , c , d , e It is a constant. T S For discrete time steps, S a , S b , S c , S d These represent the switching states of the four half-bridges. C 1. C 2 is the output capacitor. L 1. L 2 represents inductance. V dc1 , V dc2 It is a constant voltage; Based on the voltage prediction values ​​under different switch combinations, the cost value corresponding to different switch combinations is obtained using a pre-constructed cost function; wherein, the cost function is constructed based on the voltage prediction values ​​and the target output voltage. The switch combination with the lowest cost is selected as the control signal for each switch in the next cycle. By periodically executing the above process, model predictive decoupling control of TAB-PFC is achieved.

2. The TAB-PFC model prediction decoupling control method as described in claim 1, characterized in that, The cost function is specifically expressed as follows: in, , The predicted voltage of the TAB-PFC output at time k+1. , The target output voltage.

3. The TAB-PFC model prediction decoupling control method as described in claim 1, characterized in that, The target output voltage is calculated specifically by: based on the relationship between the positive and negative pole transmission power and the line current of the ring bipolar DC distribution network system, and based on the given value of the positive and negative pole line transmission power, calculating the target output voltage of TAB-PFC.

4. The TAB-PFC model prediction decoupling control method as described in claim 1, characterized in that, The different combinations of switches for the four half-bridges are specifically defined as follows: the switches for the four half-bridges are { S a , S b , S c , S d },in,{ S a , S b , S c , S d The switch state combination of} consists of {0000}, {0001}, {0010}, {0011}, {0100}, {0101}, {0110}, {0111}, {1000}, {1001}, {1010}, {1011}, {1100}, {1101}, {1110}, {1111}.

5. A TAB-PFC model predictive decoupling control system, characterized in that, include: The data acquisition unit is used to periodically sample the output voltage and inductor current of the ring bipolar DC distribution network system at the current moment and calculate the target output voltage. The ring bipolar DC distribution network system includes a TAB-PFC converter. The voltage prediction value acquisition unit is used to obtain the voltage prediction values ​​of the four half-bridges under different switching combinations in the TAB-PFC simplified circuit based on the obtained output voltage and inductor current sampling values ​​and using the pre-built output voltage prediction model of the ring bipolar DC distribution network system. The output voltage prediction model for the ring bipolar DC distribution network system is specifically represented as follows: in, v k1 , v k2 This refers to the output voltage of the TAB-PFC. V 1. V 2 represents the receiving-end voltage of the line. a , b , c , d , e It is a constant. T S For discrete time steps, S a , S b , S c , S d These represent the switching states of the four half-bridges. C 1. C 2 is the output capacitor. L 1. L 2 represents inductance. V dc1 , V dc2 It is a constant voltage; The cost value acquisition unit is used to obtain the cost value corresponding to different switching combinations based on the voltage prediction value under different switching combinations and using a pre-constructed cost function; wherein, the cost function is constructed based on the voltage prediction value and the target output voltage. The decoupling control unit is used to select the switch combination with the lowest cost as the control signal for each switch in the next cycle. By periodically executing the above process, model predictive decoupling control of TAB-PFC is realized.

6. The TAB-PFC model prediction decoupling control system as described in claim 5, characterized in that, The cost function is specifically expressed as follows: in, , The predicted voltage of the TAB-PFC output at time k+1. , The target output voltage.

7. An electronic device, comprising a memory, a processor, and a computer program stored in the memory and running thereon, characterized in that, When the processor executes the program, it implements a TAB-PFC model prediction decoupling control method as described in any one of claims 1-4.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a TAB-PFC model prediction decoupling control method as described in any one of claims 1-4.

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