Direct-current power distribution network hybrid direct-current voltage droop control method

Abstract

The invention discloses a droop control method for hybrid DC voltage of a DC power distribution network, relates to the DC power distribution network, and aims to solve the problems that a conventional DC voltage droop control strategy is not accurate enough in power distribution and large in static voltage deviation. The offset and the slope of a droop curve can be dynamically adjusted, namely, the voltage deviation value is corrected in real time, and power distribution is rapidly adjusted so as to adapt to the change of a system load. Through complementation of the two control strategies, the hybrid voltage control strategy not only can eliminate static errors, but also can quickly respond to power fluctuation, and can achieve more flexible DC voltage control. Moreover, a result after a 750V direct-current power distribution network simulation model is built on an MATLAB / Simulink platform for simulation shows that the precision of power distribution of the direct-current power distribution network can be effectively improved, the voltage deviation of a direct-current bus is remarkably reduced, and the dynamic response capability of the system is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current distribution networks, and in particular to a hybrid direct current voltage droop control method for a direct current distribution network. Background Art

[0002] With the growth of DC load and the access of distributed power sources, the demand for DC power on the user side has gradually increased, which has promoted the development of DC distribution systems. However, the DC distribution network is still in its early stages, and many operation and control technical problems need to be optimized and solved. In-depth research and optimization of the control technology of the DC distribution system are of great significance to promoting its further development. In the DC distribution network, there is only active power. The characteristics of the DC system without inductive reactance and capacitive reactance make voltage the only indicator to measure the power balance of the DC power grid. Generally, the system stability is enhanced through master-slave control, voltage margin control, and voltage slope control. The master-slave control structure is simple, but the communication needs to be accurate and fast; voltage margin control does not require inter-station communication, but in the face of load uncertainty, its margin is difficult to quantify, and its flexibility and adaptability are insufficient; voltage slope control is droop control, which indirectly manages the voltage of the DC distribution network by adjusting the power, but it may cause the bus voltage to deviate from the rated value and produce a certain static deviation.

[0003] The selection of droop coefficient directly affects the stability and dynamic performance of the system. A large droop coefficient leads to large DC voltage fluctuations, which is beneficial to power distribution, but the system has poor dynamic performance and is sensitive to load changes. A small droop coefficient leads to small voltage fluctuations and slow dynamic response, which may lead to overvoltage. Therefore, it is very important to design a reasonable droop curve. The defects of voltage static deviation and inaccurate power distribution that occur in traditional voltage droop control require improvements to traditional droop control.

[0004] In view of this, a hybrid DC voltage droop control method for a DC distribution network is needed. Summary of the invention

[0005] In view of the problems of voltage static deviation and inaccurate power distribution in the prior art, the present invention provides a hybrid DC voltage droop control method for a DC distribution network, which can maintain the stability of the DC bus voltage and solve the problem of static voltage deviation. The specific technical solution is as follows:

[0006] A hybrid DC voltage droop control method for a DC distribution network comprises the following steps:

[0007] In a DC distribution network, when the detected DC voltage exceeds the rated voltage level, the power output is adjusted through a droop control strategy to achieve a voltage increase or decrease;

[0008] The droop control strategy adopts additional deviation compensation control, which is as follows:

[0009]

[0010] Where U dc ** is the corrected DC voltage reference value, U dc * is the DC voltage reference value, U dc is the actual DC voltage value, K i is the integration coefficient;

[0011] When the DC voltage deviates from its reference value, the deviation ΔU between the actual value of the DC voltage and the reference value is calculated. dc , and input the deviation value into the PI regulator.

[0012] Preferably, the droop control strategy adopts a UP droop curve whose slope k is in an inverse relationship with the droop coefficient K. The UP variable droop curve is composed of three droop curves. Different K values ​​are used according to the voltage margin to obtain a droop slope piecewise function, which is as follows:

[0013]

[0014] Where: 1 / K H is the DC voltage U max >U>U1The slope, 1 / K is the slope of the DC voltage U2>U>U1, 1 / K L The DC voltage is U2>U>U min The slope taken.

[0015] Preferably, the calculation formula of the droop coefficient K is as follows:

[0016] K=ΔP max / ΔU max ;

[0017] Where ΔP max is the maximum power fluctuation range, ΔU max The maximum voltage fluctuation range.

[0018] Preferably, a PI controller is also used.

[0019] Preferably, the current closed-loop transfer function under the droop control strategy is for:

[0020]

[0021] Among them, the voltage loop PI coefficient is k pu , k iu , the current loop PI coefficient is k pi , k ii , the coefficient of the deviation integral loop is k ru ,.

[0022] Preferably, the transfer function of the PI controller is:

[0023]

[0024] in,.

[0025] Preferably, the voltage loop closed-loop transfer function is as follows:

[0026]

[0027] Preferably, the closed-loop characteristic equation D(s) of the system is as follows:

[0028] D(s)=LCs 5 +(R+k pi )Cs 4 +(k ii C+k iu k pi )s 3 +Kk iu k pi s 2 +Kk iu (k ii +k ru k pi )s+Kk ru k iu k ii =0.

[0029] A computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the hybrid DC voltage droop control method for a DC distribution network as described above.

[0030] A processor is used to run a program, wherein the program executes the above-mentioned hybrid DC voltage droop control method for a DC distribution network when running.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention proposes a hybrid droop control strategy that combines DC voltage deviation compensation control and voltage margin control. By comprehensively considering the control characteristics of the translation droop curve and the variable droop curve, the offset and slope of the droop curve can be dynamically adjusted, that is, the voltage deviation can be corrected in real time and the power distribution can be quickly adjusted to adapt to changes in the system load. Through the complementarity of the two control strategies, the hybrid voltage control strategy can not only eliminate static errors, but also respond quickly to power fluctuations, and can play a more flexible role in DC voltage control. When the load fluctuation is too large and causes the DC bus voltage to exceed the rated value, the variable droop curve control will automatically adjust the slope to avoid the system from deviating significantly from the rated value, and the additional deviation voltage integral control assists the droop curve translation, reduces the static error, and promotes the DC bus voltage to return to the rated value. In general, this hybrid control strategy effectively overcomes the limitations of traditional droop control, improves the accuracy of power distribution, reduces voltage deviation, and enhances the dynamic response and stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0034] Figure 1 The main power grid topology diagram;

[0035] Figure 2 It is the topology diagram of the grid-side converter G-VSC;

[0036] Figure 3 This is the UP droop characteristic control block diagram;

[0037] Figure 4 It is the UP droop characteristic curve;

[0038] Figure 5 It is a schematic diagram of the droop curve translation control;

[0039] Figure 6 The block diagram for the improved droop translation control;

[0040] Figure 7 An improved variable slope droop control curve;

[0041] Figure 8 It is the block diagram of the improved variable slope droop control;

[0042] Fig. 9 It is the block diagram of hybrid DC voltage droop control;

[0043] Fig.10is the characteristic curve based on the hybrid DC voltage droop control strategy;

[0044] Fig.11 is the block diagram of the DC voltage transfer function;

[0045] Fig.12 It is a schematic diagram of the roots of the K1 characteristic equation;

[0046] Fig.13 Schematic diagram of the roots of the K2 characteristic equation. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0049] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0050] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0051] This embodiment is based on Figure 1 The DC distribution network shown is used as a background for explanation. Its structure is a two-terminal DC distribution network topology with a bus level of 750V, including two-terminal AC power grids, energy storage systems, load units, and distributed power supply systems.

[0052] 1) Photovoltaic power generation unit: Photovoltaic PV modules input power to the grid through the converter P-DC, and Ppv is the power provided by photovoltaic to the grid. PV modules are equivalent substitutes after multiple photovoltaic arrays are connected in parallel. Photovoltaic power generation adopts MMPT control strategy.

[0053] 2) Grid-connected converter: connected to the AC grid through the converter G-VSC, Pgrid1 and Pgrid2 are the power exchanged between the AC grid and the DC distribution network. When the DC distribution network is connected to the grid, the G-VSC adopts droop control.

[0054] 3) Energy storage system: The battery and supercapacitor are connected in parallel, collectively referred to as the energy storage system. They are connected to the DC distribution network through the bidirectional DC / DC converter B-DC, and Pbat is the exchange power between the grid and the energy storage system. The energy storage uses droop control and G-VSC to control the DC bus voltage. The AC load uses the fixed AC voltage control strategy through L-VSC; the DC load uses the fixed DC voltage control strategy through L-DC.

[0055] 4) Load unit: DC loads need to be connected to the DC distribution network through DC / DC; AC loads need to be connected to the DC distribution network through AC / DC.

[0056] The AC grid is connected to the DC distribution network via a voltage source converter G-VSC. The converter structure selects a three-phase two-level VSC topology. Its circuit principle structure is as follows: Figure 2 shown.

[0057] Among them, the VSC state equation can be described as:

[0058]

[0059] Where: i d and i q The d-axis component and q-axis component of the AC current are respectively; u sd and u sq They are the d-axis component and q-axis component of the AC power grid electromotive force; u cd and u cq They are the d-axis component and q-axis component of the converter output voltage respectively.

[0060] Assume that the a-axis in the abc three-phase stationary coordinate system coincides with the d-axis in the dq synchronous rotating coordinate system, and its power can be expressed as:

[0061]

[0062] When the loss is not taken into account, the power on both sides of the converter is conserved, and P G =P dc . Among them, P G , P dc It is expressed as:

[0063]

[0064] P dc =u dc i dc

[0065] Where: P G is the grid-side power, P dc is the DC side power. At this time, the connection between the DC current and the VSC AC current components in the dq coordinate system can be established. As shown in the following formula:

[0066]

[0067] For the grid-connected converter, based on the UP DC voltage droop control strategy, the error signal e generated can be expressed as:

[0068] e=k u (U dcref -U dc )+k p (P ref -P)

[0069] According to the above formula, the UP droop control block diagram can be drawn, as shown in Figure 3 shown.

[0070] The droop control strategy of the converter can be achieved by adjusting the proportional coefficient k u , k p To achieve different control modes: when k u ≠0 and k p ≠0, the controller operates in UP droop control. u =1 and k p = 0, or k u = 0 and k p =1, the controller operates in constant DC voltage control or active power control. u =K, k p =1.

[0071] Under the condition of stable system operation, the error signal e generated by the droop controller is zero. At this time, the relationship between the system DC voltage and active power can be expressed as follows:

[0072]

[0073] When calculating the droop coefficient K, it is necessary to assume the power margin or voltage margin of the converter station. Here, the maximum power and minimum power are used to calculate the maximum and minimum values ​​of the droop coefficient K. Figure 4 shown.

[0074] When distributing power, the converter has a maximum power that can be output, which must meet the following conditions:

[0075] K≤K

[0076] max

[0077] At the same time, the minimum power should also be limited and should meet the following requirements:

[0078] K≥K min

[0079] From the UP droop characteristic curve, we can see that:

[0080]

[0081] Similarly:

[0082]

[0083] according to Figure 4 It can be seen that the selection of the droop coefficient directly affects the stability and dynamic performance of the system. A large droop coefficient leads to large DC voltage fluctuations, which is beneficial to power distribution, but the system has poor dynamic performance and is sensitive to load changes. A small droop coefficient leads to small voltage fluctuations and slow dynamic response, which may cause overvoltage. Therefore, it is very important to design a reasonable droop curve.

[0084] Traditional voltage droop control has defects such as voltage static deviation and inaccurate power distribution, which require improvement of traditional droop control. Currently, there are two basic improvement directions: droop curve translation and droop curve slope change.

[0085] Droop curve shift control is a control strategy for adjusting the droop curve shift, which aims to maintain the stability of the DC bus voltage and solve the static voltage deviation problem. Figure 5 shown.

[0086] In a DC distribution network, when the detected DC voltage exceeds the rated voltage level, the power output is adjusted through a droop control strategy to achieve a voltage increase or decrease. To achieve a parallel droop curve, the present invention adopts an additional deviation compensation control, the expression of which is:

[0087]

[0088] Where U dc ** is the corrected DC voltage reference value, U dc * is the DC voltage reference value, U dc is the actual DC voltage value, K i is the integration coefficient:

[0089] From the above formula, we can know that when the DC voltage deviates from its reference value, by calculating the deviation ΔU between the actual value of the DC voltage and the reference value dc , and input the deviation value into the PI regulator. dc If it is positive, the droop curve shifts upward, if it is negative, it shifts downward, and the signal is then added to the original voltage reference value Udc *, and obtain the new updated DC voltage reference value U dc **. The characteristic of this compensation control method is that it provides a continuous control signal instead of a discrete correction value, can smoothly adjust the voltage reference value, reduce the voltage shock caused by power mutation, and help reduce the deviation of DC voltage, thereby improving the stability and dynamic performance of the entire system.

[0090] The improved droop curve translation controller structure diagram is as follows: Figure 6 shown.

[0091] However, the disadvantage of the above method is that when the system power changes significantly, if the droop coefficient K is not adjusted accordingly, the voltage may exceed the rated value. To avoid this situation, the system needs to have a mechanism to dynamically adjust the droop coefficient K to adapt to different power changes.

[0092] In a DC distribution network, when the load power increases and causes the DC voltage to deviate from the set range, the droop curve slope control strategy will automatically adjust the droop coefficient K, making the power output more sensitive to voltage changes, responding quickly to power differences, and reducing large voltage fluctuations, which can effectively improve the system's adaptability and stability. Figure 7 shown.

[0093] Note that the slope k of the UP droop curve is inversely proportional to the droop coefficient K, that is, slope k = 1 / K. For the convenience of expression, the droop coefficient K is used here.

[0094] Depend on Figure 3-11 It can be seen that the UP droop curve is actually composed of three sections of droop curves (section I, section II, and section III). From the perspective of voltage margin, the DC voltage U1>U>U2, at this time, it works within the normal operating range, and the active power output of the converter station and the DC voltage basically maintain a constant relationship. The converter station adopts the section II droop curve; when the DC voltage U max >U>U1, the active power to be absorbed by the system is too high, causing the DC voltage to be too high. At this time, the converter station adopts the I-section droop curve; when the DC voltage U2>U>U min When the system is running at low voltage due to insufficient active power, the converter station adopts the droop curve of section III.

[0095] according to Figure 7 , different K values ​​are used according to the voltage margin, called f(U dc ) is the droop slope piecewise function, which is expressed as follows:

[0096]

[0097] Where: 1 / K H is the DC voltage U max >U>U1The slope, 1 / K is the slope of the DC voltage U2>U>U1, 1 / K L The DC voltage is U2>U>U min According to the obtained droop slope piecewise function, the structural block diagram of the droop curve variable slope controller can be derived as follows: Figure 8 shown.

[0098] It can be seen that the UP variable droop control changes the droop characteristics by dynamically adjusting the slope coefficient K, controlling the system's response speed and amplitude to voltage fluctuations, thereby adapting to different voltage and power conditions. However, the defect of the variable droop curve slope control strategy is that there is a certain degree of voltage deviation.

[0099] Aiming at the limitations of the existing DC voltage control strategy in static error elimination and power fluctuation response, the present invention further studies a new hybrid DC voltage droop control strategy, such as Fig. 9 shown.

[0100] according to Fig. 9 It can be seen that this strategy can dynamically adjust the offset and slope of the droop curve by comprehensively considering the control characteristics of the translation droop curve and the variable droop curve, that is, to correct the voltage deviation in real time and quickly adjust the power distribution to adapt to changes in the system load. Through the complementarity of the two control strategies, the hybrid voltage control strategy can not only eliminate static errors, but also quickly respond to power fluctuations, and can play a more flexible role in DC voltage control.

[0101] According to the hybrid DC voltage control strategy proposed in Section 2.3, the present invention is based on the DC distribution network designed in Section 2, and selects a DC bus voltage of 750V, a voltage fluctuation range of ±5%, a maximum of ±30V, a rated power of 40kW for converter station 1, and a rated power of 80kW for converter station 2. According to the droop coefficient K calculation formula:

[0102] K=ΔP max / ΔU max

[0103] Where ΔP max is the maximum power fluctuation range, ΔU max The maximum voltage fluctuation range.

[0104] Assume that converter station 1 uses the traditional droop curve k1 = 40e3 / 60. After using the improved droop control curve, the droop coefficient K1 = 40e3 / 60. When ΔU dc When ΔU is less than 10V, the droop coefficient increases to 1.1 times of the original value, i.e. 1.1×40e3 / 60; when 20V>ΔU dcWhen ΔU is greater than 10V, the droop coefficient increases to 1.2 times of the original value, i.e. 1.2×40e3 / 60. dc When the voltage is greater than 20V, the droop coefficient increases to 1.5 times of the original value, that is, 1.5×40e3 / 60.

[0105] In order to reflect the power distribution relationship of the droop coefficient, the converter station 2 adopts the traditional droop curve when k2 = 20e3 / 60. After adopting the improved droop control curve, the droop coefficient is set to K2 = 20e3 / 60. When ΔU dc When ΔU is less than 10V, the droop coefficient K2 increases to 1.1 times of the original value, i.e. 1.1×20e3 / 60; when 20V>ΔU dc When ΔU is greater than 10V, the droop coefficient K2 increases to 1.2 times of the original value, i.e. 1.1×20e3 / 60. dc When the voltage is greater than 20V, the droop coefficient K2 increases to 1.5 times of the original value, that is, 1.5×20e3 / 60.

[0106] According to the designed hybrid DC voltage control, its approximate UP characteristic curve is as follows Fig.10 As shown, converter station 1 is taken as an example. In order to increase a certain power margin and facilitate the comparison of the hybrid droop control strategy, the original curve K1=40e3 / 60 is not used at a voltage of 740V~760V, but K1=1.1×40e3 / 60 is used.

[0107] In order to verify the effectiveness of the designed hybrid droop control DC voltage control strategy, it is necessary to carry out mathematical modeling and analysis of the strategy to ensure the stability and reliability of the system.

[0108] According to the converter mathematical model and the hybrid droop control DC voltage control strategy, we can get Fig.11 The block diagram of the DC voltage transfer function based on UP droop is shown.

[0109] The transfer function of the PI controller is:

[0110]

[0111] The transfer function of the integral controller is:

[0112]

[0113] Assume the voltage loop PI coefficient is k pu , k iu, The current loop PI coefficient is k pi , k ii , the coefficient of the deviation integral loop is k ru To simplify the system modeling and analysis process, when the switching frequency is high, the amplification factor K is selected. PWM is 1, and the scale parameter k is takenpu =0.

[0114] First simplify the current inner loop, and then get the current closed-loop transfer function under the hybrid droop control strategy: for:

[0115]

[0116] According to u dc / u dcref Get the closed-loop transfer function for:

[0117]

[0118] After expansion, the voltage loop closed-loop transfer function is obtained: for:

[0119]

[0120] The voltage loop obtained according to the above formula Transfer function, it is easy to know that the closed-loop characteristic equation D(s) of the system is:

[0121] D(s)=LCs 5 +(R+k pi )Cs 4 +(k ii C+k iu k pi )s 3 +Kk iu k pi s 2 +Kk iu (k ii +k ru k pi )s+Kk ru k iu k ii =0.

[0122] According to the Routh stability criterion, there are no missing terms in the characteristic equation, and all coefficients are greater than 0. The Routh array of the above equation is:

[0123]

[0124] In order to facilitate the subsequent calculation and verification of the effectiveness of the proposed control strategy, Table 1 lists in detail the parameters of each component in the system, the voltage level and the correlation coefficient of the control link.

[0125] Table 1 Main control parameters of the system

[0126] parameter Numeric unit <![CDATA[Current loop k pi > 120 — <![CDATA[Current loop k ii > 15 - <![CDATA[Voltage loop k iu > 50 — <![CDATA[Adjunct integral ring k ru > 8 — Rated AC voltage 380 V Rated DC voltage 750 V Filter inductor L 0.006 H Equivalent resistance R 0.015 Ω DC link capacitor C 2000 μF

[0127] G1 and G3 are calculated by the same Rous array criterion. To simplify the calculation, the formulas that must be positive are removed. To make the system stable, the elements in the first column of the Rous array must be greater than 0, so:

[0128]

[0129] It can be seen that the amount of calculation is too large. Here, the droop coefficients are substituted into the calculation respectively. The droop coefficients K1=40e3 / 60 and K2=20e3 / 60 are substituted into the above formula respectively, and both meet the Routh stability criterion.

[0130] At the same time, in MATLAB, K1 = 40e3 / 60, K2 = 20e3 / 60 are substituted into the closed-loop characteristic equation of the system to verify the stability of the designed hybrid droop control system. Its characteristic root is as follows Fig.12 and Fig.13 As shown. It can be seen that the five characteristic roots of the above two characteristic equations are all on the negative semi-axis.

[0131] In summary, through Routh stability criterion and characteristic equation analysis, the droop coefficient designed in the present invention can ensure the stability of the voltage of the DC distribution network system.

[0132] In order to test whether the proposed strategy can improve its voltage stability and reliability, a MATLAB / Simulink Figure 1 The main parameters are set as follows: the rated power of VSC1 is 40kW, the droop coefficient K1 = 40e3 / 60; the rated power of VSC2 is 80kW, the droop coefficient K2 = 20e3 / 60; because each converter station uses the same command value for the grid voltage, the integral coefficient k of the deviation compensation control of VSC1 is ru1 =8, integral coefficient k of deviation compensation control of VSC2 ru2 = 8. The following is a simulation analysis.

[0133] At the beginning of the simulation, the constant power DC load L DC1 Power consumption 20kW, resistive DC load L DC2 Power consumption 20kW, total DC load L DC 40kW; AC load L AC The power consumption is 10kW; there are two photovoltaic arrays, each with a power of 20kW, and the total photovoltaic power is 40kW; the steady-state working voltage is 753V. At 1s, the light is enhanced, and each photovoltaic array increases by 20kW, the total system power increases by 40kW, and the voltage rises to 765V. After 2s, the light is restored, and each photovoltaic array decreases by 20kW, the total system power decreases by 40kW, and the voltage returns to 753V; at 3s, the resistive DC load LDC2 When the voltage drops to 747V after adding 20kW, the resistive DC load L DC2 Reduce 10kW and increase voltage to 750V.

[0134] Those of ordinary skill in the art will appreciate that the units of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition of each example has been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0135] In the embodiments provided by the present invention, it should be understood that the division of units is only a logical function division, and there may be other division methods in actual implementation, for example, multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored, etc.

[0136] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0137] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-0nlyMemory), random access memory (RAM, RandomAccessMemory), mobile hard disk, magnetic disk or optical disk, etc., which can store program code.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A hybrid DC voltage droop control method for a DC distribution network, characterized in that: The following steps are involved: In a DC distribution network, when the detected DC voltage exceeds the rated voltage level, the power output is adjusted through a droop control strategy to achieve a voltage increase or decrease; The droop control strategy adopts additional deviation compensation control, which is as follows: Where U dc ** is the corrected DC voltage reference value, U dc * is the DC voltage reference value, U dc is the actual DC voltage value, K i is the integration coefficient; When the DC voltage deviates from its reference value, the deviation ΔU between the actual value of the DC voltage and the reference value is calculated. dc , and input the deviation value into the PI regulator.

2. A DC distribution network hybrid DC voltage droop control method according to claim 1, characterized in that: The droop control strategy adopts the inverse relationship between the slope k of the UP droop curve and the droop coefficient K. The UP variable droop curve is composed of three droop curves. Different K values ​​are used according to the voltage margin to obtain a droop slope piecewise function, which is as follows: Where: 1 / K H is the DC voltage U max >U>U1The slope, 1 / K is the slope of the DC voltage U2>U>U1, 1 / K L The DC voltage is U2>U>U min The slope taken.

3. A DC distribution network hybrid DC voltage droop control method according to claim 2, characterized in that: The calculation formula of the droop coefficient K is as follows: K=ΔP max / ΔU max ; Where ΔP max is the maximum power fluctuation range, ΔU max The maximum voltage fluctuation range.

4. A DC distribution network hybrid DC voltage droop control method according to claim 3, characterized in that: It also includes the use of a PI controller.

5. A DC distribution network hybrid DC voltage droop control method according to claim 4, characterized in that: The current closed-loop transfer function under the droop control strategy for: Among them, k pu , k iu is the voltage loop PI coefficient, k pi , k ii is the current loop PI coefficient, K is the droop coefficient, C is the DC side capacitance, unit is μF; L is the filter inductance, unit is H; R is the equivalent resistance, unit is Ω.

6. A DC distribution network hybrid DC voltage droop control method according to claim 4, characterized in that: The transfer function of the PI controller is: Among them, k p , k i is the PI proportional coefficient.

7. A DC distribution network hybrid DC voltage droop control method according to claim 5, characterized in that: Voltage loop closed loop transfer function as follows: In the formula, k ru is the coefficient of the deviation integration loop, k pu , k iu is the voltage loop PI coefficient, k pi , k ii is the current loop PI coefficient, K is the droop coefficient, C is the DC side capacitance, unit is μF; L is the filter inductance, unit is H; R is the equivalent resistance, unit is Ω.

8. A DC distribution network hybrid DC voltage droop control method according to claim 7, characterized in that: The closed-loop characteristic equation of the system D(s) is as follows: D(s)=LCs 5 +(R+k pi )Cs 4 +(k ii C+k iu k pi )s 3 +Kk iu k pi s 2 +Kk iu (k ii +k ru k pi )s+Kk ru k iu k ii =0.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the hybrid DC voltage droop control method for a DC distribution network according to any one of claims 1 to 8.

10. A processor, characterized in that: The processor is used to run a program, wherein the program, when running, executes the hybrid DC voltage droop control method for a DC distribution network according to any one of claims 1 to 8.

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