Bus voltage regulation and power allocation method for DC microgrid considering power constraints

Abstract

The present invention discloses a bus voltage regulation and power distribution method of a DC microgrid considering power constraints, and the method can be applied to a DC microgrid system in which a plurality of power supply nodes with output power constraints and connected in parallel supply power to the bus. The method disclosed by the present invention receives an output power instruction and a bus voltage reference value, generates the output voltage required by the power supply node through three steps of voltage deviation quantization feedback, output power compensation, and output power tracking, realizes the bus voltage to be stable at the reference value, and ensures that the power supply node is not overloaded by constraining the power reference value. The method only requires quantized voltage tracking error feedback, and the minimum information transmission amount is only 1 bit. The method proposed by the present invention is independent of the load type and load size, does not require the true value of the microgrid transmission line conductivity, only requires its upper bound, and can achieve the control target for any allowable bus voltage and initial state. Under the action of the control algorithm, the closed-loop system has a plug-and-play feature and is suitable for most DC microgrid systems.

Description

Technical Field

[0001] The present invention belongs to the field of direct current microgrid control, and in particular, relates to a technology for regulating the bus voltage of a direct current microgrid with transmission line impedance and distributing power at power supply nodes by dynamically adjusting the output power and output voltage of power supply nodes. Background Art

[0002] With the continuous advancement of renewable energy generation technology, the proportion of distributed power nodes in the total power generation capacity continues to increase. Especially in the isolated microgrid, distributed power nodes are the main source of energy. Effective control of them is the basis for ensuring the normal operation of the microgrid. In the DC microgrid in the isolated operation mode, multiple power nodes are connected in parallel to supply power to the bus through transmission lines with impedance. The DC microgrid system structure is as follows: Figure 1 In this system, bus voltage regulation and power distribution are two basic control tasks. Bus voltage regulation is to adjust the output power or voltage of the power node to keep the bus voltage at the reference value when the bus voltage deviates from the reference value due to factors such as transmission line loss and mismatch between power generation and power consumption. Power distribution is to specify the size or proportion of the output power of each node based on factors such as the power generation capacity, energy storage level, and power cost of the power generation node, so that the load power can be shared by multiple power nodes.

[0003] At present, the power distribution mainly adopts the droop control method, which assumes that the power supply voltage is the same and realizes power distribution by adjusting the droop coefficient (i.e., virtual impedance) of each voltage source. Since this scheme directly specifies the ratio of output power and has no constraints on the absolute power size, considering that the output power of the system power supply node has saturation constraints, when the load power is large, this method cannot effectively avoid power overload and the safety of the system cannot be guaranteed. In addition, in order to solve the problem of bus voltage drop during the droop control process, secondary control must be introduced to compensate for voltage deviation. Therefore, the system requires a central control node to uniformly dispatch all power supply nodes, which increases the complexity of the system. In addition, when the central node fails, the system cannot work normally, which reduces the scalability of the system and the robustness to node failures.

[0004] Based on the above analysis, for DC microgrids with power constraints on power supply nodes, finding a bus voltage regulation and power distribution method that can effectively solve the above problems has significant engineering significance. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art, solve the bus voltage regulation and power distribution problems in a DC microgrid containing multiple power supply nodes connected in parallel to supply power to the bus and the power supply nodes having output power constraints, and provide a bus voltage regulation and power distribution method for a DC microgrid taking power constraints into account.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A bus voltage regulation and power allocation method for a DC microgrid considering power constraints is applied to a DC microgrid system in which a plurality of power supply nodes with output power constraints and connected in parallel supply power to the bus.

[0008] Among them, for each power node i in the DC microgrid system, i = 1, 2, ..., N, N is the number of power nodes, the output power instruction defines the recommended output power and is a piecewise continuous function, let express defines the rate of change within the domain, and yes The upper bound of the rate of change; the actual output power of the power node is P oi (t), the actual maximum output power is

[0009] The bus voltage measurement value V(t) and the bus voltage reference value V * The difference is quantified to obtain the feedback signal e(t), which is defined as:

[0010]

[0011] According to the actual output power P of the power node oi (t) and the feedback signal e(t) dynamically calculate the power compensation value required to maintain the bus voltage t is time;

[0012] Determine the required output voltage V at the power node i (t),

[0013]

[0014] in, is the maximum estimated value of the transmission line impedance, and V * is the bus voltage reference value.

[0015] Furthermore, satisfy

[0016]

[0017] in, is a differential operator, k is any is a real number, and sign(·) is a sign function.

[0018] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the steps of the bus voltage regulation and power distribution method of the DC microgrid considering power constraints.

[0019] The present invention also provides a computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of the bus voltage regulation and power distribution method of the DC microgrid considering power constraints are implemented.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0021] 1. The power allocation method disclosed in the present invention realizes the zero-error tracking of the bus voltage to the bus voltage reference value, and can respond to the output power specified value of each power node by the upper layer unit;

[0022] 2. The power tracking mode of the power allocation method disclosed in the present invention ensures that the output power of all power supply nodes in the DC microgrid system does not exceed the maximum power, and the implementation of the power constraint does not require the participation of the upper-level unit, which can ensure the safe operation of the DC microgrid system;

[0023] 3. The method proposed in the present invention adopts voltage deviation quantization feedback, and only 1 bit of information transmission is required to adjust the bus voltage to the voltage reference value, and less measurement data information is required;

[0024] 4. The method proposed in the present invention does not require communication between power supply nodes and has a plug-and-play feature;

[0025] 5. The method proposed in the present invention is adjusted by output power, which is independent of the load type and size, does not require the true value of the microgrid transmission line conductance, and can be widely applied to various existing DC microgrid systems;

[0026] 6. The method proposed in the present invention can achieve the control target for any allowable bus voltage, system initial value and voltage detection quantizer, and the parameter selection is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A structural diagram of a DC microgrid system considered for the present invention;

[0028] Figure 2 This is the output voltage curve of the power node in the experiment;

[0029] Figure 3 It is the reference value of the output power of the power node in the experiment;

[0030] Figure 4 It is the actual output power curve of the power node in the experiment;

[0031] Reference numerals: 101 - transmission line equivalent resistance, 102 - bus bar, 103 - load DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] For satisfaction Figure 1 The DC microgrid system shown in the figure contains a DC microgrid experimental platform with three distributed power sources. The resistances from the power node to the bus are 3Ω, 3Ω and 1.5Ω respectively. The bus voltage reference value is set to 55V, the constant power load is 80W, and the upper limit of the output power of the power node is 50W.

[0034] Figure 1 The DC microgrid system includes a plurality of distributed power supply nodes 104 connected in parallel, each distributed power supply node 104 includes a DC buck-boost module and an energy storage battery, and a transmission line equivalent resistor 101 and a load 103 are included between the distributed power supply node 104 and the bus 102.

[0035] To apply the bus voltage regulation and power distribution method disclosed in the present invention, the following steps need to be performed:

[0036] 1. The method disclosed in the present invention takes into account the output power constraint of the power supply node and sets the upper limit of the power supply output power according to the hardware design parameters of the experimental platform. Estimation of the upper bound of transmission line conductance

[0037] 2. This method is independent of load type and load size, and does not require the true value of the transmission line conductance, but only its upper bound; on this experimental platform, the actual transmission line conductance is 1 / 3, 1 / 3, and 2 / 3;

[0038] 3. Set the bus voltage reference value V * =55;

[0039] 4. Power node output power instruction i=1,2,3, respectively From this it can be estimated that

[0040] 5. Order express defines the rate of change within the domain, and yes The upper limit of the rate of change; for a given output power command The total output power of the power node may not match the load power, causing the bus voltage to deviate from the preset value V * To this end, for each power node, the voltage deviation quantization feedback e(t) and power compensation value are constructed Its structure is

[0041]

[0042] in, is a differential operator, k is any is a real number, and sign(·) is a sign function.

[0043] In this example, k=80 is selected; it should be noted that all parameters in this range are valid, and the larger the k, the faster the bus voltage converges to the reference value, but the larger the voltage ripple; the method proposed in the present invention uses the quantitative feedback of the difference between the bus voltage and the voltage reference value to dynamically adjust the power compensation value And by the power compensation value The derivative control is used to limit the output power to maintain The use of voltage deviation quantized feedback reduces the information required for feedback control, and only 1 bit of information feedback is needed to achieve the control target.

[0044] 6. According to the output power instruction And power compensation value Computable

[0045]

[0046] and calculate the required output voltage

[0047]

[0048] 7. V i (t) is used as the output voltage reference value of power node i, and V is realized through the DC buck-boost circuit at the output end of the power node. i (t) voltage output;

[0049] By implanting steps 5-7 into the embedded memory of the power node, the bus voltage can be tracked to the reference value through real-time calculation by the processor, and the overload of the power node can be prevented.

[0050] from Figure 2 It can be seen from the power node and bus voltage curve shown in FIG. 1 that the bus voltage of the system can track the desired voltage of 55V by using the method proposed in the present invention. The output power reference value of each power node is as follows: Figure 3 In the initial stage, under the action of power compensation, the output power reference value continues to rise. When the bus voltage reaches the reference value, it fluctuates under the influence of the power command issued by the upper control unit. Figure 4 The actual output power of each power node is shown in Figure 2. It can be seen that the output power of all power nodes is greater than 0 and less than 50W, indicating that the output power of all power nodes in the system under the saturation constraint is within the allowable range and there is no overload phenomenon.

[0051] Preferably, the embodiment of the present application also provides a specific implementation of an electronic device capable of implementing all steps in the bus voltage regulation and power distribution method of a DC microgrid considering power constraints in the above embodiment, and the electronic device specifically includes the following contents:

[0052] Processor, memory, communication interface and bus; the processor, memory and communication interface communicate with each other through the bus; the communication interface is used to realize information transmission between server-side devices, metering devices and user-side devices and other related devices.

[0053] The processor is used to call the computer program in the memory, and when the processor executes the computer program, all the steps in the bus voltage regulation and power distribution method of the DC microgrid considering power constraints in the above embodiment are implemented.

[0054] An embodiment of the present application also provides a computer-readable storage medium capable of implementing all steps of the bus voltage regulation and power distribution method for a DC microgrid considering power constraints in the above-mentioned embodiment. A computer program is stored on the computer-readable storage medium. When the computer program is executed by a processor, all steps of the bus voltage regulation and power distribution method for a DC microgrid considering power constraints in the above-mentioned embodiment are implemented.

[0055] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the hardware + program embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0056] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0057] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0058] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0059] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, a person of ordinary skill in the art can also make many forms of specific changes under the guidance of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A bus voltage regulation and power distribution method for a DC microgrid considering power constraints, characterized in that: Applicable to a DC microgrid system in which a plurality of power nodes with output power constraints and connected in parallel supply power to a bus; Among them, for each power node i in the DC microgrid system, i = 1, 2, ..., N, N is the number of power nodes, the output power instruction defines the recommended output power and is a piecewise continuous function, let express defines the rate of change within the domain, and yes The upper bound of the rate of change; the actual output power of the power node is P oi (t), the actual maximum output power is The bus voltage measurement value V(t) and the bus voltage reference value V * The difference is quantified to obtain the feedback signal e(t), which is defined as: According to the actual output power P of the power node oi (t) and the feedback signal e(t) dynamically calculate the power compensation value required to maintain the bus voltage t is time; Determine the required output voltage V at the power node i (t), in, is the maximum estimated value of the transmission line conductance, and V * is the bus voltage reference value.

2. The bus voltage regulation and power distribution method of a DC microgrid considering power constraints according to claim 1 is characterized in that: satisfy in, is a differential operator, k is any is a real number, and sign(·) is a sign function.

3. An electronic 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 program, the steps of the bus voltage regulation and power distribution method of the DC microgrid considering power constraints as described in any one of claims 1 to 2 are implemented.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the bus voltage regulation and power distribution method of a DC microgrid considering power constraints as described in any one of claims 1 to 2 are implemented.

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