Voltage control method, device and equipment for auxiliary power supply of direct-current power distribution network and medium

Abstract

The invention relates to the technical field of direct-current power distribution networks, in particular to a voltage control method, device and equipment for an auxiliary power supply of a direct-current power distribution network and a medium. The method comprises the steps of obtaining an auxiliary power supply circuit topological structure, and determining a constraint condition of a transformer transformation ratio; constructing a state space model of the output voltage of the auxiliary power supply according to the constraint condition, discretizing the state space model according to a preset control time step length to obtain a discrete model, and predicting the output voltage of the discrete model by using a forward Euler method; and subtracting the predicted output voltage from the reference voltage, constructing a cost function of the output voltage of the system, and performing real-time control on the transformer by taking the minimum cost function as a target. According to the method, the state space model of the output voltage of the auxiliary power supply is constructed according to the constraint condition, the model prediction control mode has the characteristic of real-time optimization, model prediction control is adopted, the optimal duty ratio is obtained through the cost function, and rapid dynamic response and stable output voltage of the auxiliary power supply can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current distribution network, and in particular to a voltage control method, device, equipment and medium for an auxiliary power supply of a direct current distribution network. Background Art

[0002] With the rapid development of new energy sources such as solar photovoltaic and wind power generation, DC distribution network is gradually becoming an important part of the power system. DC distribution network has the advantages of high energy transmission efficiency, compatibility with renewable energy and flexible control. In view of the problem that DC distribution network does not rely on external AC power supply to provide auxiliary power supply for primary power equipment and power detection and monitoring equipment, it is necessary to design an auxiliary power supply suitable for DC distribution network. At present, single-ended flyback converter is widely used as auxiliary power supply for power electronic systems such as photovoltaic inverters, uninterruptible power supplies, frequency converters and charging modules due to its simple structure and low cost.

[0003] The input voltage level of the DC distribution network is relatively high, and the rated voltage of the power equipment used is relatively low. The converter needs to achieve a high step-down ratio, and the voltage stress of the converter switch tube also increases accordingly. This not only affects the selection of switching devices, but also reduces the efficiency of the auxiliary power supply. The traditional flyback converter is no longer suitable for the auxiliary power supply of the DC distribution network.

[0004] The auxiliary power supply exhibits nonlinear characteristics due to the periodic switching of the switch state of the switch tube. The traditional PID control method realizes control by approximately linearizing the system, which has poor control effect on the system and cannot achieve rapid dynamic response and stable output voltage of the auxiliary power supply.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0006] The present invention provides a voltage control method, device, equipment and medium for an auxiliary power supply of a direct current distribution network, thereby effectively solving the problems in the background technology.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a voltage control method of an auxiliary power supply of a DC distribution network, comprising the following steps:

[0008] Obtain the auxiliary power supply circuit topology and determine the transformer ratio constraints;

[0009] Constructing a state space model of the auxiliary power supply output voltage based on the constraint conditions, discretizing the state space model with a preset control time step to obtain a discrete model, and predicting the output voltage of the discrete model using the forward Euler method;

[0010] The predicted output voltage is subtracted from the reference voltage to construct a cost function of the system output voltage, and the transformer is controlled in real time with the minimum cost function as the goal.

[0011] Furthermore, the constraints of the transformer ratio include:

[0012]

[0013] Where n is the ratio of the transformer primary winding N1 to the secondary winding N2; V in is the system input voltage, V o is the output voltage, D max is the maximum duty cycle, V Dmax is the reverse withstand voltage of the diode, V DSmax The maximum withstand voltage of the switch tube.

[0014] Furthermore, constructing a state space model of the auxiliary power supply output voltage includes:

[0015]

[0016] In the formula, C o is the output capacitor, S is the on and off state of the switch tube, defined as 1 and 0, I S is the secondary output current of the transformer.

[0017] Furthermore, the state space model is discretized with a preset control time step to obtain a discrete model, including:

[0018]

[0019] Where k is the preset control time step, I s (k) is the secondary output current of the transformer, I p (k) is the primary input current of the transformer.

[0020] Further, the predicting the output voltage of the discrete model by using the forward Euler method includes:

[0021] When S(k)=0, I s When (k) is not 0, the predicted voltage V o (k+1):

[0022]

[0023] When S(k)=1, I s When (k) is 0, the predicted voltage V o (k+1):

[0024]

[0025] Where S(k) is the control signal with k as the preset control time step.

[0026] Furthermore, the subtraction of the predicted output voltage from the reference voltage to construct a cost function of the system output voltage includes:

[0027] J=|V o (k+1)-V Ref |;

[0028] In the formula, J is the cost function, V o (k+1) is the predicted output voltage, V Ref is the reference voltage.

[0029] The present invention also includes a voltage control device for an auxiliary power supply of a DC power distribution network, using the above method, the device comprising:

[0030] A constraint unit, used to obtain the auxiliary power supply circuit topology and determine the constraint conditions of the transformer ratio;

[0031] A discrete modeling unit, configured to construct a state space model of the auxiliary power supply output voltage based on the constraint conditions, discretize the state space model with a preset control time step to obtain a discrete model, and predict the output voltage of the discrete model using a forward Euler method;

[0032] The control unit is used to make a difference between the predicted output voltage and the reference voltage, construct a cost function of the system output voltage, and perform real-time control on the transformer by minimizing the cost function.

[0033] The present invention also includes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described above is implemented.

[0034] The present invention also includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0035] The beneficial effects of the present invention are as follows: by constructing a state space model of the auxiliary power supply output voltage with constraint conditions, and discretizing the state space model with a preset control time step to obtain a discrete model, the output voltage of the discrete model is predicted using the forward Euler method, and the model predictive control method has the characteristics of real-time optimization. By using the model predictive control, the optimal duty cycle is obtained through the cost function, so that the auxiliary power supply can achieve rapid dynamic response and stable output voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 is a flow chart of the method in Example 1;

[0038] Figure 2 It is a structural schematic diagram of the device in Example 1;

[0039] Figure 3 is a circuit topology diagram of the auxiliary power supply in Example 2;

[0040] Figure 4 is a flowchart of the method in Example 2;

[0041] Figure 5 It is a structural schematic diagram of the computer device of the present invention. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0043] Embodiment 1:

[0044] like Figure 1 As shown: A voltage control method for an auxiliary power supply of a DC distribution network comprises the following steps:

[0045] Obtain the auxiliary power supply circuit topology and determine the transformer ratio constraints;

[0046] A state space model of the auxiliary power supply output voltage is constructed based on constraint conditions, and the state space model is discretized with a preset control time step to obtain a discrete model, and the output voltage of the discrete model is predicted using the forward Euler method;

[0047] The predicted output voltage is subtracted from the reference voltage to construct the cost function of the system output voltage, and the transformer is controlled in real time with the goal of minimizing the cost function.

[0048] By constructing a state space model of the auxiliary power supply output voltage based on constraints and discretizing the state space model with a preset control time step, a discrete model is obtained. The output voltage of the discrete model is predicted using the forward Euler method. The model predictive control method has the characteristics of real-time optimization. By using model predictive control, the optimal duty cycle is obtained through the cost function, which can achieve rapid dynamic response and stable output voltage of the auxiliary power supply.

[0049] In this embodiment, the constraints of the transformer ratio include:

[0050]

[0051] Where n is the ratio of the transformer primary winding N1 to the secondary winding N2; V in is the system input voltage, V o is the output voltage, D max is the maximum duty cycle, V Dmax is the reverse withstand voltage of the diode, V DSmax The maximum withstand voltage of the switch tube.

[0052] :Construct the state space model of the auxiliary power supply output voltage, including:

[0053]

[0054] In the formula, C o is the output capacitor, S is the on and off state of the switch tube, defined as 1 and 0, I S is the secondary output current of the transformer.

[0055] The state space model is discretized with a preset control time step to obtain a discrete model, including:

[0056]

[0057] Where k is the preset control time step, I s (k) is the secondary output current of the transformer, I p (k) is the primary input current of the transformer.

[0058] As a preferred embodiment of the above, the output voltage of the discrete model is predicted by using the forward Euler method, including:

[0059] When S(k)=0, I s When (k) is not 0, the predicted voltage V o (k+1):

[0060]

[0061] When S(k)=1, I sWhen (k) is 0, the predicted voltage V o (k+1):

[0062]

[0063] Where S(k) is the control signal with k as the preset control time step.

[0064] The predicted output voltage is subtracted from the reference voltage to construct the cost function of the system output voltage, including:

[0065] J=|V o (k+1)-V Ref |;

[0066] In the formula, J is the cost function, V o (k+1) is the predicted output voltage, V Ref is the reference voltage.

[0067] like Figure 2 As shown, this embodiment also includes a voltage control device for an auxiliary power supply of a DC distribution network, using the above method, the device includes:

[0068] A constraint unit, used to obtain the auxiliary power supply circuit topology and determine the constraint conditions of the transformer ratio;

[0069] A discrete modeling unit is used to construct a state space model of the output voltage of the auxiliary power supply with constraint conditions, discretize the state space model with a preset control time step to obtain a discrete model, and predict the output voltage of the discrete model using the forward Euler method;

[0070] The control unit is used to make a difference between the predicted output voltage and the reference voltage, construct a cost function of the system output voltage, and perform real-time control on the transformer by minimizing the cost function.

[0071] Embodiment 2:

[0072] The following embodiments are only used to more clearly illustrate the technical solution of this embodiment, and are not intended to limit the protection scope of this embodiment.

[0073] like Figure 3 As shown, it is a structural diagram of an auxiliary power supply suitable for a DC distribution network in this embodiment, including two voltage-equalizing capacitors, a transformer, two switching tubes, three diodes, and a filter capacitor; the two voltage-equalizing capacitors are connected in series to equalize the voltage and generate two voltages of the same magnitude;

[0074] The first switch tube is connected to the series connection point between the first primary winding of the transformer and the voltage-equalizing capacitor, and the second switch tube is connected to the second primary winding of the transformer and the negative electrode of the input voltage;

[0075] Two diodes are connected in series at the input sides of the two primary windings to block the circulating current between the branches, and one diode is connected in series at the opposite end of the second winding of the transformer to rectify.

[0076] The transformer ratio is determined by the system input voltage V in , output voltage V o , maximum duty cycle D max , diode reverse withstand voltage value V Dmax And the maximum withstand voltage of the switch tube V DSmax Constraints, the specific constraint formula is as follows:

[0077]

[0078] Where n is the ratio of the transformer primary winding N1 to the secondary winding N2;

[0079] The filter capacitor is connected in parallel at the output end of the auxiliary power supply to reduce the output voltage ripple and make the output voltage more stable.

[0080] like Figure 4 As shown, the specific steps of the control method adopted in this embodiment are introduced below:

[0081] First, construct the converter mathematical model, as shown in equations (2), (4), and (5):

[0082]

[0083] Among them C o is the output capacitor, S is the on and off state of the switch, defined as 1 and 0, and I S is the transformer secondary output current.

[0084] Because the finite set model predictive control is based on a preset control time step T s The discrete-time algorithm is used, so (2) must be converted into discrete mode. When t = k, the corresponding parameters are defined as the output voltage V o (k), transformer secondary output current I s (k) and transformer primary input current I p (k).

[0085] The relationship between the transformer primary input current and secondary output current is as follows

[0086]

[0087] Since the input current and output current of the transformer are related to the control signal S, the current will suddenly change. When S(k)=0, I s When (k) is not 0, the predicted voltage V in discrete mode can be obtained by using the forward Euler method. o (k+1), as shown below:

[0088]

[0089] When S(k)=1, I s When (k) is 0, the predicted voltage V in discrete mode can be obtained by using the forward Euler method. o (k+1), as shown below:

[0090]

[0091] By defining (4) and (5) as state-space models 1 and 2, the load voltage V can be predicted based on the control signal condition. o (k+1).

[0092] Further constructing the cost function, according to the model predictive control theory, the cost function J is essential for determining the optimal control action. o (k+1) and the reference voltage V Ref The cost function can be obtained by subtraction as follows:

[0093] J=|V o (k+1)-V Ref | (6)

[0094] The control action that minimizes the cost function J is the optimal control action and will be applied to the converter for real-time control.

[0095] Finally, the modulator converts the optimal duty cycle into the appropriate switching signal for each switch tube.

[0096] See also Figure 5 A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.

[0097] The embodiment of the present application further provides a storage medium 430 on which a computer program is stored. When the computer program is run by the processor 410, the above method is executed.

[0098] Among them, the storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable red-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.

[0099] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0100] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0101] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0102] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0103] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0104] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0105] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0106] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A voltage control method for an auxiliary power supply of a DC distribution network, characterized in that: The steps include: Obtain the auxiliary power supply circuit topology and determine the transformer ratio constraints; Constructing a state space model of the auxiliary power supply output voltage based on the constraint conditions, discretizing the state space model with a preset control time step to obtain a discrete model, and predicting the output voltage of the discrete model using the forward Euler method; The predicted output voltage is subtracted from the reference voltage to construct a cost function of the system output voltage, and the transformer is controlled in real time with the minimum cost function as the goal.

2. The voltage control method of the auxiliary power supply of the DC distribution network according to claim 1, characterized in that: The constraints of the transformer ratio include: Where n is the ratio of the transformer primary winding N1 to the secondary winding N2; V in is the system input voltage, V o is the output voltage, D max is the maximum duty cycle, V Dmax is the reverse withstand voltage of the diode, V DSmax The maximum withstand voltage of the switch tube.

3. The voltage control method of the DC distribution network auxiliary power supply according to claim 2, characterized in that: The constructing of the state space model of the auxiliary power supply output voltage comprises: In the formula, C o is the output capacitor, S is the on and off state of the switch tube, defined as 1 and 0, I S is the secondary output current of the transformer.

4. The voltage control method of the auxiliary power supply of the DC distribution network according to claim 3, characterized in that: The step of discretizing the state space model with a preset control time step to obtain a discrete model includes: Where k is the preset control time step, I s (k) is the secondary output current of the transformer, I p (k) is the primary input current of the transformer.

5. The voltage control method of the auxiliary power supply of the DC distribution network according to claim 4, characterized in that: The predicting the output voltage of the discrete model by using the forward Euler method includes: When S(k)=0, I s When (k) is not 0, the predicted voltage V o (k+1): When S(k)=1, I s When (k) is 0, the predicted voltage V o (k+1): Where S(k) is the control signal with k as the preset control time step.

6. The voltage control method of the auxiliary power supply of the DC distribution network according to claim 1, characterized in that: The step of subtracting the predicted output voltage from the reference voltage to construct a cost function of the system output voltage includes: J=|V o (k+1)-V Ref |; In the formula, J is the cost function, V o (k+1) is the predicted output voltage, V Ref is the reference voltage.

7. A voltage control device for an auxiliary power supply of a DC distribution network, characterized in that: Using the method according to any one of claims 1 to 6, the device comprises: A constraint unit, used to obtain the auxiliary power supply circuit topology and determine the constraint conditions of the transformer ratio; A discrete modeling unit, configured to construct a state space model of the auxiliary power supply output voltage based on the constraint conditions, discretize the state space model with a preset control time step to obtain a discrete model, and predict the output voltage of the discrete model using a forward Euler method; The control unit is used to make a difference between the predicted output voltage and the reference voltage, construct a cost function of the system output voltage, and perform real-time control on the transformer by minimizing the cost function.

8. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 6 is implemented.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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