A method and device for designing control parameters of a source-side converter of a direct-current microgrid considering current limiting

Abstract

The application provides a DC micro-grid source-side converter control parameter design method and device considering current amplitude limiting. The method comprises the following steps: obtaining circuit parameters of a DC micro-grid, sudden power of a constant power load and current amplitude limiting threshold of a source-side converter; establishing a bus voltage transient response model under load sudden change considering current saturation nonlinear characteristics; based on the model and second-order system equivalence, deducing an analytical relationship between bus voltage transient drop amplitude and source-side converter voltage outer loop control bandwidth and bus capacitance; taking that bus voltage does not collapse as a constraint condition, combining the analytical relationship with the current amplitude limiting threshold, calculating a feasible region of control parameters and circuit parameters meeting system large signal stability; and performing quantitative parameter design or checking on the source-side converter according to the parameter feasible region. The application provides a design-oriented analytical criterion, effectively avoids bus voltage collapse caused by current amplitude limiting, and improves operation stability of the DC micro-grid under large disturbance working conditions.

Description

Technical Field

[0001] This invention relates to the field of DC power distribution and DC microgrid stability control technology, and in particular to a method and apparatus for designing control parameters of DC microgrid source-side converters that take current limiting into account. Background Technology

[0002] DC microgrids are widely used in scenarios such as data center power supply, ship power systems, and campus power distribution due to their advantages such as easy access to new energy sources, flexible energy routing, and compact system structure. In DC microgrids, converters are often used on the load side to achieve voltage or power stabilization, forming a constant power load; at the same time, the source-side converters typically employ cascaded control of the voltage outer loop and the current inner loop, and current limiting thresholds are set to meet the current stress constraints and protection requirements of the devices.

[0003] Under conditions of large disturbances such as sudden increases in load power, constant power loads exhibit equivalent negative impedance characteristics, which can easily lead to bus voltage drops and oscillations. When the source-side converter current reaches the limiting threshold, the control system enters the saturation region, and the power that the source side can provide is limited. The bus voltage may experience a continuous decline and converge to a low-voltage operating point, resulting in instability. The above-mentioned instability mechanism is closely related to "current limiting saturation—source-load power mismatch—insufficient bus energy" and is coupled with parameters such as source-side control parameters, bus capacitance, current limiting threshold, and load surge amplitude.

[0004] In engineering applications, a sustained drop in the bus voltage or convergence to a low operating point may trigger DC load undervoltage protection, downstream converter shutdown, or protection actions, leading to power outages and interruptions to critical loads. Simultaneously, prolonged current-limited saturation of the source-side converter increases thermal stress and current ripple, reducing efficiency and shortening lifespan; in severe cases, it may even induce cascading failures and system shutdowns. Therefore, the "nonlinear large-disturbance stability problem introduced by current-limited saturation" needs to be clearly defined as an engineering design problem. In the parameter design phase, a quantitative assessment and constraint of the minimum transient bus voltage should be established, providing parameter boundaries that can be directly used for tuning and verification.

[0005] In existing technologies, parameter tuning for DC microgrid stability often employs small-signal stability analysis or time-domain simulation trial-and-error methods. The former struggles to address the nonlinear large disturbances introduced by current-limiting saturation, while the latter relies heavily on extensive simulations or experimental screening, lacking large-signal stability design criteria and parameter feasible domain expressions that can be directly applied to engineering design and rapid verification. Therefore, there is an urgent need for a technical solution that can quantitatively establish the relationship between "source-side control parameters—bus transient minimum voltage—stability constraint boundary" and output the feasible domain under the most unfavorable operating condition of a given load change, to guide the selection and configuration of source-side converter parameters. Summary of the Invention

[0006] This invention aims to address the problem in existing technologies that, when considering source-side converter current limiting saturation and large disturbances under constant power loads, lack large-signal stability criteria and feasible regions for control parameters suitable for engineering design. Unconstrained parameter tuning can lead to significant bus voltage drops or even collapse, undervoltage power loss in critical loads, and frequent protection trips. This invention, by outputting feasible regions and boundary-based criteria, enables quantitative design and rapid verification of source-side converter parameters, thereby reducing the risk of significant low-voltage bus voltage drops and instability under sudden increases in load power.

[0007] The innovative aspects of this invention include at least: (1) For DC microgrid engineering applications, the saturated nonlinear constraints introduced by the current limiting protection of the source-side converter are explicitly incorporated into the large-signal modeling and criteria; (2) Under the given most unfavorable load power sudden change condition, establish a quantitative relationship between “source side control parameters / bus capacitance / current limiting threshold - bus transient minimum voltage”; (3) Based on the maximum available power boundary under the source-side current limiting condition, construct a large-signal stability constraint boundary that can be directly verified, and form a set of parameter inequality constraints; (4) Solve and output the feasible domain of control parameters and / or circuit parameters that satisfy the large signal stability constraint, so as to generate parameter configuration or verification instructions, realize boundary-oriented design, and reduce reliance on a large number of simulation trials.

[0008] To achieve the above objectives, this invention provides a method for designing control parameters for a source-side converter in a DC microgrid that takes current limiting into account. This method is applied to a DC microgrid with a source-side converter, wherein the source-side converter is configured with a current limiting threshold. The method includes: Step 1: Obtain the input parameters for parameter design and determine the range of candidate parameters. The input parameters shall include at least the bus voltage reference value. Bus capacitor Constant power load power before sudden change in load power After a sudden change in load power, the constant power load power and current limiting threshold And determine the candidate range of the outer loop control parameters for the source-side converter voltage; Step 2: Taking into account the current limiting threshold Introducing nonlinear saturation constraints, the bus voltage is established under the condition of sudden load power change. An equivalent model of the transient response is derived, and equivalent dynamic model parameters for characterizing the transient response are obtained from the equivalent model. These equivalent dynamic model parameters include at least the natural angular frequency. With damping ratio ; Step 3: Calculate the transient minimum value of the bus voltage based on the equivalent dynamic model parameters. or peak value of transient voltage drop at the bus ,in ; Step 4: Establish large-signal stability constraint boundaries and substitute the given values ​​into the equation. The stable constraint boundary yields the parametric constraint conditions; The stability constraint boundary satisfies:

[0009] The aforementioned stability constraint boundary reflects the constraint that when the source-side current reaches the limiting threshold, the minimum transient voltage of the bus must meet the constraint that the power that the source side can provide is not less than the load power.

[0010] Preferably, the system can be divided into an ideal dynamic model that ignores current limiting and a saturated nonlinear dynamic model that takes current limiting into account. The transient minimum value of bus voltage and the corresponding feasible region of control parameters obtained by the two types of models under the same power disturbance conditions can be compared. This can intuitively reveal the mechanism of feasible region shrinkage caused by current limiting, which is convenient for engineers to make conservative selections and quick verifications.

[0011] Step 5: Solve the feasible region of source-side converter control parameters that satisfy the large-signal stability constraint based on the parameter constraints, and output the feasible region to generate selection, configuration or verification instructions for source-side converter control parameters, so as to update the voltage outer loop proportional coefficient and integral coefficient, thereby reducing the risk of a large drop in bus voltage.

[0012] Furthermore, the transfer function of the voltage outer loop controller satisfies:

[0013] in This is the voltage outer loop proportionality coefficient. This represents the voltage outer loop integral coefficient.

[0014] Furthermore, the equivalent second-order dynamic model satisfies: ,

[0015] in, It is the outer ring ratio coefficient. The voltage outer loop integral coefficient, This refers to the bus capacitor.

[0016] Furthermore, the transient drop peak value satisfies:

[0017] in This represents the change in bus current caused by sudden changes in load power. The peak value of the equivalent second-order system step response; at the damping ratio Use the corresponding preset constants to facilitate engineering applications.

[0018] This invention also provides a device for designing control parameters of a source-side converter in a DC microgrid that takes current limiting into account. The device is characterized by its applicability to a DC microgrid comprising a low-voltage bus, a source-side converter, and a constant-power load. The device includes: The acquisition module is used to acquire the parameter design input parameters and determine the range of candidate parameters. The input parameters include at least the following: Bus capacitor Power parameters before and after load power change and as well as And determine the range of possible control parameters; The modeling module is used to establish an equivalent model of the transient response of the low-voltage bus voltage, taking into account the nonlinear saturation constraints introduced by the current limiting threshold, and to obtain the equivalent dynamic model parameters. The calculation module is used to calculate the transient characteristic quantity of the bus voltage based on the equivalent dynamic model parameters. The transient characteristic quantity includes at least the transient minimum value of the bus voltage or the transient drop peak value. The constraint module is used to establish large-signal stability constraint boundaries and generate parametric constraint conditions; The solution output module is used to solve for the feasible region of control parameters based on the parameter constraints and output the feasible region of control parameters, and to generate selection, configuration or verification instructions for the source-side converter control parameters.

[0019] The present invention also provides a terminal device and a computer-readable storage medium, wherein a computer program running thereon is used to implement the above-described method.

[0020] The above-described solution of the present invention has the following beneficial effects: 1. Taking into account the current limiting saturation nonlinear constraints, establish a quantitative relationship between the bus transient minimum voltage and parameters under the most unfavorable working condition of load power sudden change, and give the large signal stability constraint boundary so that the selection of control parameters has a criterion that can be directly verified.

[0021] 2. The output of control parameters that satisfy the large signal stability constraints can be used for the rapid design, configuration and verification of source-side converter parameters, reducing the workload of relying on a large number of simulation trials.

[0022] 3. The feasible region and its boundary can be used for rapid screening and margin assessment during the engineering design phase, avoiding bus voltage collapse due to overly aggressive control parameters or improper current limiting threshold configuration; at the same time, it can significantly shorten the parameter tuning cycle, reduce simulation / experiment costs, and improve the power supply continuity and operational reliability of the system under large disturbances.

[0023] 4. By selecting appropriately , , and This can reduce the risk of significant voltage drop and instability on the bus when the load increases suddenly, and improve the stability and reliability of DC microgrid power supply. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the design method for the control parameters of a DC microgrid source-side converter considering current limiting, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the DC microgrid structure involved in the embodiments of the present invention; Figure 3 This is a schematic diagram of the source-side converter control structure involved in an embodiment of the present invention; Figure 4 This is a schematic diagram of the input voltage-current characteristics of the load converter and the stable / unstable phase trajectory of the system involved in the embodiments of the present invention; Figure 5 This is a schematic diagram of the stable / unstable waveforms of the bus voltage and the source-side converter inductor current involved in the embodiments of the present invention; Figure 6 This is a schematic diagram of the feasible domain of control parameters involved in the embodiments of the present invention; Figure 7 This is a structural block diagram of the device provided in an embodiment of the present invention; Figure 8 This is a structural block diagram of a terminal device provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of a computer-readable storage medium structure provided in an embodiment of the present invention; Figure 10 This is a structural block diagram of another terminal device provided in an embodiment of the present invention. Detailed Implementation

[0025] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a locking connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] This invention addresses existing problems by providing a method and apparatus for designing control parameters of a DC microgrid source-side converter that takes current limiting into account.

[0030] (I) System Structure and Variable Definition

[0031] like Figure 2 As shown, a DC microgrid includes at least: a source-side converter, a low-voltage bus, and a bus capacitor. And constant power loads. The source-side converter is used to feed energy from the upstream DC bus to the low-voltage bus and regulate the low-voltage bus voltage.

[0032] The source-side converter adopts a cascaded control structure of voltage outer loop and current inner loop, such as... Figure 3 As shown, the transfer function of the voltage outer loop controller satisfies:

[0033] in , These are the proportional coefficient and integral coefficient of the outer voltage loop, respectively.

[0034] Low-voltage bus voltage reference value is The low-voltage bus voltage is The bus current is The power of a constant power load before and after a sudden change in load power are respectively... and The source-side converter is set with a current limiting threshold. Used to limit the inductor current of the source-side converter. No more than .

[0035] (II) Method and Flow

[0036] like Figure 1 As shown, the parameter feasible domain determination method of the present invention includes steps 1 to 5, as detailed below.

[0037] Step 1: Obtain design input parameters and determine the range of candidates.

[0038] Get , , , , Input parameters and determine the outer loop voltage parameters. , The range of candidates. Input parameters can come from system design specifications, device selection, and protection constraints.

[0039] Step 2: Establish an equivalent transient response model considering current-limiting saturation.

[0040] Taking into account the saturation nonlinearity introduced by current limiting, the bus voltage under the condition of sudden load power change is established. The transient response equivalent model is proposed. Preferably, under the condition that the bandwidth of the inner current loop is much larger than the bandwidth of the outer voltage loop, the voltage transient is simplified by equivalent means, and the voltage transient element is characterized as an equivalent second-order dynamic model.

[0041] The parameters of the equivalent second-order dynamic model satisfy: ,

[0042] And the natural frequency can be further obtained. .

[0043] Step 3: Calculate the transient characteristic quantities of the low-voltage bus voltage under load power disturbance conditions based on the equivalent dynamic model parameters. The transient characteristic quantities include at least the minimum transient value of the bus voltage. or peak value of transient voltage drop at the bus Specifically, it includes: 1. Determine the power disturbance and equivalent current disturbance: Obtain the power parameters of a constant power load before and after the disturbance. and And determine the power disturbance:

[0044] Based on the bus voltage at the instant the disturbance occurs (which can be taken as...) (or steady-state bus voltage before disturbance) to determine the equivalent current disturbance on the bus side Preferably:

[0045] 2. Determine the equivalent second-order model parameters using control parameters and bus capacitance: When the bus voltage transient response is equivalent to a second-order dynamic model, based on the source-side converter voltage outer loop scaling factor... Integral coefficient With bus capacitor Determine the natural angular frequency With damping ratio For example, satisfying: ,

[0046] 3. And the natural frequency can be further obtained:

[0047] Calculate the transient peak and transient minimum values: Based on the peak coefficient of the step response of the second-order system Calculate the peak value of the transient voltage sag at the bus:

[0048] This yields the transient minimum value of the bus voltage:

[0049] 4. Method for determining the peak value coefficient: The peak coefficient Damping ratio The damping ratio can be determined and obtained through analytical calculation, table lookup, or fitting function calculation; When taking the preset value, the Use the corresponding preset constants to facilitate rapid engineering calculations.

[0050] Step 4: Establish large-signal stability constraint boundaries and generate constraint conditions

[0051] A large-signal stability constraint boundary is established based on the current limiting threshold and load power disturbance parameters, and the transient characteristic quantities are substituted to obtain the parameter constraint conditions, specifically including: 1. Establish large-signal stability constraint boundaries: When the inductor current of the source-side converter reaches the current limiting threshold Subsequently, the maximum power that the source side can supply to the bus is limited. To prevent the bus voltage from continuously dropping and entering a low-voltage operating state, the minimum transient bus voltage is maintained. The source-side available power must be no less than the constant power load power. Thus, the large-signal stability constraint boundary is obtained:

[0052] 2. Substitute into the transient characteristic generation parameter inequality: The result obtained in step 3:

[0053] Substituting the above stability constraint boundary and combining it with:

[0054] Get about , , and The set of parameter constraint inequalities; where , and Depend on , Sure.

[0055] 3. Solve for and output the feasible region of the parameters: The feasible region of source-side converter control parameters that satisfies the large-signal stability constraint is obtained by solving the set of parameter constraint inequalities. The feasible region of parameters is output in at least one of the following forms: inequality constraint set, boundary curve / surface, parameter interval, or lookup table data, and is used to generate instructions for selecting, configuring, or verifying the source-side converter control parameters.

[0056] (III) Implementation Examples (Parameter Selection Examples)

[0057] Taking a typical low-voltage DC bus system as an example, the bus reference voltage is taken as... The current limiting threshold is taken as Bus capacitor ; Load power is from Mutation to .

[0058] 1. Calculate based on steps 3 and 4. Substituting the stability constraint boundary, we obtain the result that satisfies... Parameter constraints; further, based on step 5, output the feasible region and determine... The lower limit is then determined by:

[0059] Determine the range of values ​​for the outer loop PI parameter to complete the parameter design and configuration.

[0060] 2. Explanation of stable / unstable phase trajectories: like Figure 4 As shown, a constant power load exhibits approximately constant power characteristics on the bus side through a load converter: when the bus voltage drops, the load input current increases to maintain constant power, exhibiting a negative incremental impedance characteristic. After the source-side converter current reaches the limiting threshold, the source-side output current is limited, and the instantaneous power supply available to the bus decreases as the bus voltage decreases, thus forming the most unfavorable operating condition under large disturbances.

[0061] Based on the above mechanism, the system typically has a high-voltage operating point and a low-voltage operating point in the phase plane (bus voltage - source-side inductor current): when the control parameters are within the feasible region obtained by this invention, the disturbed phase trajectory will return to the high-voltage operating point (stable trajectory) after the current limiting is lifted; when the parameters exceed the feasible region, the phase trajectory will continue to evolve towards the low voltage direction along the current limiting boundary and eventually enter the low-voltage operating state (instability trajectory), corresponding to the bus voltage collapse phenomenon.

[0062] In the ideal model that ignores current limiting, the source-side converter can provide sufficient current for a short time, and the bus voltage transient is mainly determined by the closed-loop second-order dynamics. The state trajectory after the disturbance tends towards the high-voltage operating point throughout the operating range. However, in the actual model that considers current limiting, when the state trajectory touches the current-limiting boundary, the available current on the source side is clamped, and its maximum available power decreases as the bus voltage decreases. This may form a positive feedback loop of "further decrease in supply capacity - continued decrease in bus voltage," causing the trajectory to evolve towards the low-voltage operating point. Therefore, the stability constraint boundary given in step 4 of this invention can be equivalently understood as the critical boundary of the stable operating domain of the finite current-limited system. It is more conservative than the ideal model, but can be directly calculated through analytical criteria without the need for extensive time-domain simulation trials.

[0063] (III) Time-domain waveform verification

[0064] like Figure 5 As shown, two sets of outer-loop PI parameters were selected: one set within the feasible region and the other set outside the feasible region. The bus voltage and source-side converter inductor current waveforms were compared under the same load power step condition. When within the feasible region, although the inductor current may trigger current limiting and plateau segment, the minimum value of the bus voltage is still higher than the stability constraint critical boundary, and subsequently the bus voltage recovers to near the reference value. When outside the feasible region, the inductor current saturates at the current limiting threshold for a long time, the available power on the source side is insufficient to support a constant power load, the bus voltage continues to decrease and enters a low-voltage operating state, verifying the effectiveness of the stability constraint boundary established in step 4.

[0065] (iv) Display of feasible region of control parameters

[0066] For different combinations of operating parameters (e.g., different bus capacitances, different pre-disturbance power levels, etc.), this invention calculates the corresponding critical bandwidth lower limit based on the stability criterion. To verify the effectiveness of the criterion, two sets of control bandwidth parameters, one below and one above the critical bandwidth lower limit, were selected for comparative testing under each operating condition. The results show that when the bandwidth is below the lower limit, the bus voltage exhibits a collapse trend, while when the bandwidth is above the lower limit, the bus voltage can recover and stabilize, thus verifying the guiding role of the criterion of this invention in parameter selection.

[0067] like Figure 6 As shown, by combining the expression for the transient minimum value of the bus voltage obtained in step 3 with the large-signal stability constraint boundary obtained in step 4, a set of constraint inequalities regarding the voltage outer loop PI parameters and bus capacitance, etc., can be obtained. Solving this set of inequalities yields the feasible region of the control parameters: any combination of parameters within the feasible region satisfies the constraint that "the power available at the source side at the transient minimum bus voltage is not less than the load power," thus ensuring that the bus voltage does not collapse under large disturbances. Optionally, the small-signal stability or dynamic performance constraints can be superimposed with the above large-signal constraints to form the final parameter selection region that can be used for engineering tuning.

[0068] (v) Implementation methods of devices and terminal equipment

[0069] like Figure 1 As shown, this embodiment of the invention provides a method for designing parameters of a source-side converter in a DC microgrid that takes current limiting control into account. It is applied to a DC microgrid system that includes a source-side converter, a DC bus capacitor, and a constant power load (CPL). It is used to determine the feasible domain of source-side converter control parameters (e.g., voltage outer loop PI parameters) and / or bus capacitor parameters under load power abrupt change (large disturbance) conditions, thereby avoiding bus voltage collapse and improving large signal stability.

[0070] The DC microgrid system includes at least: an input voltage source (e.g., source-side bus voltage). Source-side Buck converter, DC bus capacitor Source-side converter inductor DC bus voltage Bus current Source-side inductor current and load branches exhibiting constant power characteristics via a DC / DC interface; the source-side converter sets a current limiting threshold. Used to restrict Or its current command does not exceed the stated limiting threshold.

[0071] Step 1: Obtain system parameters and disturbance conditions, and determine the parameters to be designed.

[0072] Obtain or determine the bus voltage reference value Bus capacitor Source-side inductor Input voltage Current limiting threshold Circuit parameters, etc. Obtain or determine the power level of the constant power load before and after the disturbance, denoted as the power level before the disturbance as... After the disturbance And the disturbance type was determined to be a large disturbance scenario such as "load connection / load power step jump"; Determine the source-side converter control structure, including at least a voltage outer loop controller. With current inner loop controller Preferably:

[0073] Step 1 is used to obtain the circuit parameters, control parameters and disturbance conditions of the target system, providing input for subsequent transfer function derivation and criterion calculation.

[0074] Step 2: Equivalently convert the power step to a bus current step to obtain the equivalent disturbance: Step 2 is used to transform the "load power surge" into an "equivalent current step disturbance" that is easy to analyze and calculate, and includes at least the following: At the instant the disturbance occurs, the bus voltage can be approximated by a reference value. (Or take the steady-state bus voltage before the disturbance), thus converting the power disturbance into an equivalent bus current disturbance; The equivalent bus current step disturbance amplitude can be obtained as follows:

[0075] Step 2 converts the power disturbance into a current disturbance, enabling the minimum bus voltage to be directly calculated based on the bus voltage transfer function.

[0076] Step 3: Establish the closed-loop transfer function of the bus voltage and extract the second-order equivalent parameters: Based on the source-side converter control model, the bus voltage can be expressed as a superposition of the reference input and the bus current disturbance input:

[0077] Due to the step change in load power It usually remains constant, therefore:

[0078] in It is the closed-loop transfer function from bus current disturbance to bus voltage disturbance.

[0079] When the bandwidth of the inner current loop is significantly greater than the bandwidth of the outer voltage loop, the effect of the current loop on voltage transients can be ignored, making... It can be simplified to a second-order form:

[0080] The second-order equivalent parameters can be obtained from the control parameters and the capacitance parameters:

[0081] Step 4: Calculate the transient minimum value of the bus voltage and fit the peak value coefficient: Step 4 is used to obtain the minimum bus voltage from the second-order response. And by fitting, complex expressions are engineered, including at least: (1) Calculate the transient minimum value of the bus voltage: Get from step 2 Substituting into step 3 yields We obtain the time-domain expression for the bus voltage disturbance and extract its first peak value (corresponding to the lowest voltage point). Therefore, the minimum bus voltage can be expressed as:

[0082] in The peak coefficient, which is related to the damping ratio, typically has an exact formula that includes exponential and inverse trigonometric functions, making it inconvenient to implement in engineering.

[0083] (2) Padé approximation and least squares fitting of peak coefficients: To facilitate engineering calculations and rapid online / offline solutions, this embodiment of the invention introduces a fitting module. To approximate; using the Padé approximation Approximating a first-order rational function, the parameters of the approximation function are optimized using the least squares method to obtain the fitted expression:

[0084] Thus, the engineering calculations can be obtained directly. The relationship between expressions and parameter constraints.

[0085] Step 5: Based on the power supply boundary caused by current limiting, construct stability constraints and output the feasible region of parameters: When the source-side current reaches the limit At this time, the maximum available power on the source side is related to the bus voltage; to prevent the bus voltage from continuously dropping and entering the low-voltage operating point, the minimum bus voltage must not be less than the critical boundary.

[0086] The result obtained in step 4 Substituting into the above formula, we get about , , , , as well as The set of inequality constraints; The feasible region of parameters is solved and output based on the constraint set. The output form can be parameter interval, boundary curve / surface, or lookup table data, which is used to guide the tuning of source-side converter control parameters and the selection of bus capacitors. Optionally, the lower limit constraint of large signal stability and the upper limit constraint of small signal stability are superimposed to obtain the final feasible parameter region that "neither collapses the large signal nor oscillates the small signal".

[0087] like Figure 7 As shown, the present invention also provides a feasible domain determination device 700 for large-signal stability control parameters of a low-voltage bus in a DC microgrid, taking into account current limiting. This device is applied to a DC microgrid scenario including a low-voltage bus, a source-side converter, and a constant-power load. The source-side converter is configured with a current limiting threshold to limit its output current or current reference to a preset limit value. The device 700 is used to output the feasible domain of source-side converter control parameters and / or circuit parameters that satisfy large-signal stability constraints under large disturbance conditions of sudden load power changes, and is used to generate parameter configuration or verification instructions.

[0088] The acquisition module 701 is used to acquire the input parameters for parameter design and determine the candidate range; the input parameters include at least: the rated / reference voltage of the low-voltage bus, the bus capacitance, the constant power load power parameters before and after the load power change, the power disturbance amount, and the current limiting threshold of the source-side converter; and to determine the candidate range of the outer loop control parameters of the source-side converter voltage.

[0089] Modeling module 702 is used to establish an equivalent model of the transient response of low-voltage bus voltage under the condition of sudden change in load power, taking into account the saturated nonlinear constraint introduced by the current limiting threshold, and to obtain equivalent dynamic model parameters for characterizing the transient response from the equivalent model; the equivalent dynamic model parameters include at least one or more of the following: natural angular frequency, damping ratio, and control bandwidth; preferably, under the condition that the bandwidth of the inner current loop is much larger than the bandwidth of the outer voltage loop, the voltage transient element is equivalent to a second-order dynamic model to facilitate analytical calculation.

[0090] The calculation module 703 is used to calculate the transient characteristic quantity of the bus voltage based on the equivalent dynamic model parameters; the transient characteristic quantity includes at least the transient minimum value of the bus voltage or the transient peak value of the bus voltage; wherein, the calculation module 703 may further include: a disturbance calculation unit, used to determine the power disturbance quantity from the power before and after the load power change, and to determine the equivalent current disturbance quantity from the bus voltage at the moment the disturbance occurs; a transient response calculation unit, used to calculate the step response peak coefficient from the equivalent second-order dynamic model, and thereby obtain the transient peak value and the transient minimum value.

[0091] The constraint module 704 is used to establish a large-signal stability constraint boundary and substitute the transient characteristic quantity into the stability constraint boundary to obtain parameter constraint conditions. The stability constraint boundary reflects that when the source-side current reaches the limiting threshold, the power that the source side can provide is limited. In order to avoid the bus voltage from continuously dropping into the low-voltage operating point, the constraint relationship of "the power that the source side can provide at the lowest transient bus voltage is not lower than the load power" must be satisfied, thereby forming a set of constraint inequalities about control parameters, bus capacitance and current limiting threshold.

[0092] The solution output module 705 is used to solve for the feasible region of source-side converter control parameters that satisfies the large-signal stability constraint based on the parameter constraint conditions, and output the feasible region of control parameters. The feasible region of parameters can be output in at least one form of inequality constraint set, boundary curve / surface, parameter interval or lookup table data, and is used to generate selection, configuration or verification instructions for source-side converter control parameters.

[0093] The sending module 706 is used to send the configuration or verification instructions to the source-side converter controller or the host computer / energy management system to update the voltage outer loop proportional coefficient and integral coefficient, and the bus capacitor selection parameters, thereby reducing the risk of large bus voltage drop and instability under sudden load power increase conditions and improving the large signal stability of the DC microgrid.

[0094] It should be noted that the information interaction and execution process between the above modules are based on the same concept as the method embodiments of this application, and their specific functions and technical effects can be found in the method embodiments section, and will not be repeated here. Those skilled in the art will understand that, for the sake of convenience and brevity, the above functional module division is used as an example. In practical applications, the above functions can be implemented by different modules as needed, or multiple modules can be integrated into the same processing unit; the integrated unit can be implemented in hardware or as a software functional unit.

[0095] like Figure 8As shown, the present invention also provides a terminal device D80, comprising: at least one processor D800, a memory D801, and a computer program D802 stored in the memory D801 and executable on the at least one processor D800. When the processor D800 executes the computer program D802, it implements the aforementioned method for designing control parameters of a DC microgrid source-side converter considering current limiting. The terminal device D80 can be a desktop computer, laptop, server, edge computing node, or cloud server, or other computing device.

[0096] It should be noted that the information interaction and execution process between the above-mentioned devices / units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, and they will not be repeated here.

[0097] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0098] like Figure 9 As shown, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements a method for designing control parameters of a DC microgrid source-side converter that takes current limiting into account.

[0099] This invention also provides a terminal device, such as... Figure 10 As shown, the terminal device D10 of this embodiment includes: at least one processor D100 ( Figure 10 The diagram shows only one processor, a memory D101, and a computer program D102 stored in the memory D101 and executable on the at least one processor D100. When the processor D100 executes the computer program D102, it implements the above-described method for designing control parameters of a DC microgrid source-side converter that takes current limiting into account.

[0100] The terminal device D10 can be a desktop computer, laptop, handheld computer, server, server cluster, or cloud server, etc. This terminal device may include, but is not limited to, a processor D100 and a memory D101. Those skilled in the art will understand that... Figure 10 This is merely an example of terminal device D10 and does not constitute a limitation on terminal device D10. It may include more or fewer components than shown in the figure, or combine certain components, or different components, such as input / output devices, network access devices, etc.

[0101] The processor D100 can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0102] In some embodiments, the memory D101 may be an internal storage unit of the terminal device D10, such as a hard disk or memory of the terminal device D10. In other embodiments, the memory D101 may be an external storage device of the terminal device D10, such as a plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, etc., equipped on the terminal device D10. Furthermore, the memory D101 may include both internal and external storage units of the terminal device D10. The memory D101 is used to store the operating system, applications, bootloader, data, and other programs, such as the program code of the computer program. The memory D101 can also be used to temporarily store data that has been output or will be output.

[0103] It should be noted that the information interaction and execution process between the above-mentioned devices / units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, and they will not be repeated here.

[0104] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0105] If the integrated unit is implemented as 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, all or part of the processes in the methods of the above embodiments of this application can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include at least: any entity or device capable of carrying the computer program code to a building device / terminal device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. Examples include USB flash drives, portable hard drives, magnetic disks, or optical disks.

[0106] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for designing control parameters for a DC microgrid source-side converter considering current limiting, characterized in that, This method is applied to a DC microgrid comprising a low-voltage bus, a source-side converter, and a constant-power load, wherein the source-side converter is equipped with a current limiting threshold to limit the output current or current reference of the source-side converter from exceeding a preset limit value; the method is used to adjust the constant-power load power before the disturbance. Step change to power after disturbance The method for determining the feasible region of source-side converter control parameters that satisfy large-signal stability constraints under load power abrupt change conditions includes: Step 1: Obtain the input parameters for parameter design. The input parameters include at least the rated voltage of the low-voltage bus. Bus capacitor Power before and after load power change and Parameters and the current limiting threshold And determine the candidate range of the outer loop control parameters for the source-side converter voltage; Step 2, taking into account the current limiting threshold. Introducing nonlinear saturation constraints, establishing the low-voltage bus voltage under conditions of sudden load power changes. The transient response equivalent model is obtained, and the equivalent dynamic model parameters used to characterize the transient response are obtained from the equivalent model. The equivalent dynamic model parameters include at least one or more of the following: natural frequency, damping ratio, and control bandwidth. Step 3: Calculate the transient characteristic quantities of the low-voltage bus voltage under the condition of sudden load power change based on the equivalent dynamic model parameters. The transient characteristic quantities include at least the minimum transient value of the bus voltage. or peak value of transient voltage drop at the bus And satisfy: Step 4, based on the current limiting threshold With load power disturbance parameters Establish a large-signal stability constraint boundary and substitute the transient characteristic quantity into the large-signal stability constraint boundary to obtain the parameter constraint condition; Step 5: Solve the feasible region of source-side converter control parameters that satisfy the large-signal stability constraint based on the parameter constraint, and output the feasible region of control parameters to generate selection, configuration or verification instructions for source-side converter control parameters; send the configuration or verification instructions to the source-side converter controller to update the voltage outer loop proportional coefficient and integral coefficient.

2. The method for designing control parameters of a DC microgrid source-side converter considering current limiting as described in claim 1, characterized in that, The large-signal stability constraint boundary in step 4 includes: in, The constant power load power after load power disturbance. This is the lowest transient value of the bus voltage. The current limiting threshold is defined as follows.

3. The method for designing control parameters of a DC microgrid source-side converter considering current limiting as described in claim 1, characterized in that, In step 2, the equivalent model of the low-voltage bus voltage transient response is simplified to an equivalent second-order dynamic model, which is based on the natural frequency. With damping ratio Characterization.

4. The method for designing control parameters of a DC microgrid source-side converter considering current limiting as described in claim 1, characterized in that, The transfer function of the source-side converter voltage outer loop controller satisfies: And the natural angular frequency With damping ratio From the above , and bus capacitors Determine and satisfy: ， in, It is the outer ring proportionality coefficient. The voltage outer loop integral coefficient, This refers to the bus capacitor.

5. A method for designing control parameters of a DC microgrid source-side converter considering current limiting, as described in claim 3 or 4, characterized in that, In step 3, the minimum transient value of the bus voltage is calculated from the transient drop peak value and satisfies: as well as in, This represents the change in bus current caused by sudden changes in load power. The peak coefficient of the step response based on the equivalent second-order dynamic model is given.

6. The method for designing control parameters of a DC microgrid source-side converter considering current limiting according to claim 5, characterized in that, The peak coefficient of the step response Damping ratio The damping ratio is determined and obtained through table lookup, analytical calculation, or function fitting; When taking the preset value, the Take the corresponding preset constant.

7. The method for designing control parameters of a DC microgrid source-side converter considering current limiting according to claim 1, characterized in that, The feasible region of the parameters is output in at least one of the following forms: a set of inequality constraints, a boundary surface, a parameter interval, or lookup table data, and is used to determine the outer loop control parameters of the source-side converter voltage. , Bus capacitor .

8. A device for designing control parameters for a DC microgrid source-side converter considering current limiting, characterized in that, The device, applicable to a DC microgrid comprising a low-voltage bus, a source-side converter, and a constant-power load, includes: The acquisition module is used to acquire the parameter design input parameters and determine the range of candidate parameters. The input parameters include at least the following: Bus capacitor Power parameters before and after load power change and as well as And determine the range of possible control parameters; The modeling module is used to establish an equivalent model of the transient response of the low-voltage bus voltage, taking into account the nonlinear saturation constraints introduced by the current limiting threshold, and to obtain the equivalent dynamic model parameters. The calculation module is used to calculate the transient characteristic quantity of the bus voltage based on the equivalent dynamic model parameters. The transient characteristic quantity includes at least the transient minimum value of the bus voltage or the transient drop peak value. The constraint module is used to establish large-signal stability constraint boundaries and generate parametric constraint conditions; The solution output module is used to solve for the feasible region of control parameters based on the parameter constraints and output the feasible region of control parameters, and to generate selection, configuration or verification instructions for the source-side converter control parameters.

9. A terminal device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the converter parameter design method as described in claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the converter parameter design method as described in claims 1 to 7.

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