Parameterization for code compatible low voltage AC microgrid controller

Abstract

The invention relates to parameterization for a code compatible low voltage AC microgrid controller. A method for operating a controller for a microgrid includes obtaining a set of parameter data characterizing one or more regulation curves of one or more state grid codes. The one or more adjustment curves are related to a set of function variables executed by the controller for a point of common coupling (PCC) function. The method also includes configuring the message to a plurality of distributed energy sources (DERs), the plurality of distributed energy sources (DERs) being interconnected to the PCC. The message is configured to read input data from a register of each DER. The method further includes executing a PCC function to control the microgrid according to at least one of the one or more regulation curves based on a subset of the input data from each DER associated with the set of function variables.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a method, apparatus, and computer-readable medium for operating a low voltage AC microgrid controller. Background Art

[0002] A microgrid is a local grid with defined electrical boundaries that acts as a single controllable entity. A microgrid can include distributed energy resources (DER) such as photovoltaic devices (PV), wind turbines, battery energy storage systems (BESS), and loads. A microgrid can operate in grid-connected mode or islanded mode. In grid-connected mode, the microgrid is connected to the traditional wide area grid (macrogrid) and operates synchronously. In islanded mode, there is no support from the wide area grid, and the microgrid operates autonomously. Microgrid configurations can be direct current (DC), alternating current (AC), or hybrid. AC microgrids can operate in conjunction with the wide area grid.

[0003] Various countries and regions around the world have developed their own grid codes for microgrids, such as the US IEEE 1547 code, the Italian CEI0-16 code, and the German VDE AR4110 code. Each grid code can specify many regulation curves for managing microgrids. Microgrid controllers need to manage DERs in the microgrid while complying with the given grid code. Microgrid controllers also need to sort the input data from DERs to obtain data relevant to managing the microgrid. Summary of the invention

[0004] Embodiments of the present disclosure provide a method for operating a controller of a microgrid. The method includes obtaining a parameter data set of one or more regulation curves characterizing one or more national grid codes. The one or more regulation curves are associated with a function variable set of a common coupling point (PCC) function executed by the controller. The method also includes configuring a message to a plurality of distributed energy resources (DERs) interconnected to the PCC. The message is configured to read input data from a register of each DER. The method also includes executing a PCC function to control the microgrid according to at least one regulation curve of the one or more regulation curves based on a subset of the input data from each DER associated with the function variable set. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The subject matter of the present disclosure will be described in more detail below based on exemplary drawings. All features described and / or illustrated herein may be used alone or in various combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following:

[0006] Figure 1 shows an exemplary structure of an AC microgrid according to some embodiments;

[0007] Figure 2 An exemplary flow chart illustrating a method of operating a microgrid controller according to some embodiments is shown;

[0008] Figure 3 Two active power versus voltage curves (Volt-Watt) of the IEEE 1547 code are shown;

[0009] Figure 4 The reactive power versus voltage curve (Volt-Var) of the IEEE 1547 code is shown;

[0010] Figure 5 The reactive power versus active power curve (Watt-Var) of the IEEE 1547 code is shown;

[0011] Figure 6 The Volt-Var curve for the Italian CEI0-16 code is shown;

[0012] Figure 7 The Volt-Var curve of the German VDE-AR4110 code is shown;

[0013] Figure 8 shows the low voltage ride through curve from the IEEE 1547 code;

[0014] Fig. 9 The low voltage ride through curve from the CEI0-16 code is shown;

[0015] Fig.10 illustrates examples of low voltage ride through and high voltage ride through according to the IEEE 1547 code according to some embodiments;

[0016] Fig.11A and 11B illustrates consecutive read messages of multiple DERs according to some embodiments;

[0017] Fig.12 shows an exemplary PQ polygon according to some embodiments;

[0018] Fig.13 is a flow chart illustrating a method of operating a microgrid controller according to some embodiments; and

[0019] Fig.14 is a simplified block diagram of a controller for controlling a microgrid according to some embodiments. DETAILED DESCRIPTION

[0020] Figure 1FIG. 1 shows an exemplary structure of an AC microgrid 100. In this example, the microgrid 100 includes a plurality of DERs, such as a PV system 110, three BESSs 120, 122, and 124 (e.g., lithium-ion batteries, lead-acid batteries, and NaNiCl batteries). 2 The DERs are interconnected via an AC bus 140. The connection point 160 is referred to as a point of common coupling (PCC). The microgrid 100 may be coupled to a wide area power grid 170. A circuit breaker 150 may be provided at the PCC 160. A microgrid controller 180 may be coupled to the PCC 160. The microgrid controller 180 may regulate the power flow from the DERs and maintain the quality and reliability of the microgrid. The power generated by the DERs is controlled according to the load demand. For example, the objectives of any control technique may include maintaining a constant voltage and a constant frequency of the microgrid.

[0021] Various countries and regions of the world have developed their own grid codes for microgrids. Exemplary grid codes include the US IEEE 1547 code, the Italian CEI0-16 code, and the German VDE AR4110 code. Each grid code can specify many regulation curves. The regulation curves characterize function variables that are important for PCC management, such as voltage, frequency, active power, reactive power, etc. Exemplary regulation curves may include reactive power relative to voltage curve (Volt-Var), reactive power relative to active power curve (Watt-Var), reactive power relative to power factor curve (PF-Var), active power relative to voltage curve (Volt-Watt), frequency drop curve, voltage ride-through curve, etc. When the regulation curves of a given grid code overlap in the control of one or more function variables, the grid code may have a priority list for setting power priority.

[0022] The microgrid controller can obtain input data from the DER by accessing the DER's registers. Each DER manufacturer can have its own register map (e.g., a Modbus register map). The Modbus register map can include a list that defines what the data is, where the data is stored (e.g., in which registers), and how the data is stored. Since the microgrid field is still in its infancy, there are currently no specific rules on which DERs can be included in the aggregated power control loop at the PCC. Currently, the microgrid controller needs to sort the various loads, sources, and storage devices on a case-by-case basis to meet the power requirements at the PCC. There is a need to streamline the function parameterization between the National Grid code and the classification process for various types of DER.

[0023] Embodiments of the present disclosure provide a method for initializing a low voltage AC microgrid controller that can be easily adapted to comply with various national grid codes and read relevant data from various DERs. A common data structure can be configured to save parameterized data representing regulation curves for various grid codes and to store register mappings for DERs to parse relevant data from DERs. The microgrid controller can dynamically reshape the aggregation boundaries of the PCC control loop as DERs enter and leave the microgrid.

[0024] It should be noted that the regulation curves of various national grid codes may have some common trends. For example, most regulation curves include piecewise linear regions, so they can be characterized by a set of endpoints that define the piecewise linear region. Some regulation curves (such as Volt-Var curves or low voltage ride-through curves) may have the same form in different national grid codes, except that the coordinate values ​​of the endpoints are different. According to some embodiments, each regulation curve can be parameterized by a set of endpoints. The parameters are stored in a common data structure defined by a set of function variables.

[0025] According to some embodiments, more prominent national grid codes (such as the US IEEE 1547 code, the Italian CEI0-16 code, and the German VDE AR4110 code) can be parameterized and preloaded into the microgrid controller as a national grid code library. Any new grid code can be parameterized by a user (e.g., an engineer) using the same general data structure and can be added to the national grid code library. The regulation curves of various grid codes tend to complement each other. When there is overlap, priorities can be set in the case structure. Complying with one grid code may not exclude the functions of another grid code.

[0026] According to some embodiments, a microgrid controller may define a set of function variables for a PCC function executed by the microgrid controller for managing the microgrid. A lookup table may be provided for linking registers of a given DER to a set of function variables. A read message may be configured to read input data at all registers. A parser may sort a larger input data set to obtain a smaller subset of input data associated with function variables (such as voltage, current, frequency, etc.) of a PCC function. Embodiments of the present disclosure may streamline the characterization process of various national grid codes and streamline the classification process of various types of DERs, which may provide robust control at the PCC while allowing organic DER growth at industrial sites.

[0027] Figure 2An exemplary flow chart illustrating a method of operating a microgrid controller 210 according to some embodiments is shown. The controller 210 is configured to run two programs in parallel. On the right, a first program (e.g., a programmable logic controller program or PLC PRG) can load tabular features from the National Grid code and set parameters for PCC functions. On the left, a second program (e.g., a Modbus program or MB PRG) can perform data acquisition using Modbus slave functions. The PLC program and the Modbus program can run at their own rates and can share data through global variables.

[0028] For example, on the right side, in 220, the PLC program can parameterize the regulation curves of one or more national grid codes, such as the US IEEE 1547 code, the Italian CEI0-16 code, the German VDE AR4110 code, etc. Some national grid codes may have multiple regulation curves. In 222, the PLC program can set the regulation curve priority among the multiple regulation curves. In 224, the PLC program can set the ride-through (RT) and trip parameters (e.g., low voltage ride-through or LVRT, high voltage ride-through or HVRT). Steps 220, 222, and 224 are initialization steps for parameterizing the national grid code, which will be described in more detail below. If it is a new grid code (or a custom code entered by the user), the parameters of the regulation curve and ride-through timer that characterize the new code can be stored in the controller 210. If the grid code has been parameterized and loaded into the controller 210, the PLC program can skip steps 222 and 224 and go to step 226.

[0029] On the left side, in 230, the Modbus program can set the IP address for the register of each DER. In 232, a lookup table can be used to map the function variables of the PCC function to the register address of each DER. Steps 230 and 232 are initialization steps for Modbus communication with the DER, which will be described in more detail below. If it is a new DER that has just entered the microgrid, the mapping data of the register address can be stored in the controller 210.

[0030] Once the initialization steps 220, 222, 224, 230, and 232 are performed, the microgrid controller 210 may run loop steps 226, 228, 234, 236, 238, and 240 to manage the microgrid. On the right side, in 226, an energy management state machine (EMSM) may select which PCC functions to run by state and user preferences (e.g., U.S. patent application serial number 18 / 363,375, entitled “ENERGY MANAGEMENT STATE MACHINE FOR MICROGRIDS,” filed on August 1, 2023, describes an EMSM, the contents of which are incorporated herein by reference). In 228, active and reactive power (PQ) deaggregation is performed to allocate active and reactive power to individual DERs. The PQ deaggregation step 228 is described in more detail below.

[0031] On the left side, in 234, the PQ aggregator is updated. For example, if a new DER has entered the microgrid, the microgrid controller 210 can update the aggregated PQ polygon characteristics and update the polling rate of the DER according to the number of devices active in the microgrid. In 236, the input data is read from the registers of each DER. The input data is parsed to obtain a subset of the input data related to the function variables of the PCC function. The input data subset is input into the EMSM 226. In 238, the Modbus channel continuously repeats its task by first polling the circuit breaker at the PCC, then polling the DER, and finally sending the command. In 240, data related to the function variables of the PCC function, such as voltage (V), frequency (f), active power (P), reactive power (Q), etc., are measured at the PCC. The PQ deaggregation step 228 can also check the state of charge (SOC) of each DER and classify it as charged, balanced, or blank, which affects the PQ aggregator as described in more detail below.

[0032] Parameterized adjustment curve

[0033] According to some embodiments, Figure 2 In step 220, the PLC program may preload the characteristics of popular national grid codes for some distributed generation sites, such as the US IEEE 1547 code, the Italian CE10-16 code, the German VDEAR4110 code, etc. Studying the various regulation curves of various grid codes, some common patterns can be observed.

[0034] Figure 3 , 4 5 and 6 show some exemplary tuning curves for IEEE 1547 codes. Figure 3 Two active power versus voltage curves (Volt-Watt) are shown; Figure 4Shows the reactive power versus voltage curve (Volt-Var); and Figure 5 Shows the reactive power versus active power curve (Watt-Var). Note that each of these regulation curves includes a number of piecewise linear regions. For example, Figure 3 Each of the Volt-Watt curves shown has a first horizontal linear region for V < V 1 , a second linear region for V 1 < V < V 2 , and a third horizontal linear region for V > V 2 . One or two endpoints define each piecewise linear region. For example, the first linear region is defined by the endpoints (P 1 , V 1 ), the second linear region is defined by the endpoints (P 1 , V 1 ) and (P 2 , V 2 ), and the third linear region is defined by the endpoints (P 2 , V 2 ).

[0035] According to some embodiments, each regulation curve can be defined by variables of the form (X, Y), such as Figure 3 The (P, V) of the Volt-Watt curve shown, Figure 4 The (V, Q) of the Volt-Var curve shown, and Figure 5 The (P, Q) of the Watt-Var curve shown. The array parser can assign endpoints to each piecewise linear region. For example, in the Volt-Watt curve shown in Figure 3 , the logic for specifying each linear region can be as follows: If X < X1, then Y = Y1; if X1 < X < X2, then Y = (X - X1)*(Y2 - Y1) / (X2 - X1); if X > X2, then Y = Y2. Here, the X variable is the voltage V, and the Y variable is the active power P. Table 1 from the IEEE 1547 code specifies the settings of the endpoints of the piecewise regions for Class A and Class B devices, such as (P 1 , V 1 ) and (P 2 , V 2 ). The grid code can include a number of settings for a given regulation curve. For example, the IEEE 1547 code includes three tables for voltage-active power settings. In some embodiments, each setting in the settings can be parameterized and stored in the controller.

[0036]

[0037] Table 1

[0038] As another example, for Figure 4 the Volt-Var curve shown, the logic for classifying each linear region can be as follows: If X < X1, then Y = Y1; if X1 < X < X2, then Y = (X - X1)*(Y2 - Y1) / (X2 - X1); if X2 < X < X3, then Y = Y2; if X3 < X < X4, then Y = (X - X3)*(Y4 - Y3) / (X4 - X3); if X > X4, then Y = Y4. Here, the X variable is the voltage V, and the Y variable is the reactive power Q. Table 2 is from the IEEE 1547 code, which specifies the settings of the endpoints of the segmented regions, such as (V 1 , Q 1 ), (V 2 , Q 2 ), (V 3 , Q 3 ), and (V 4 , Q 4 ).

[0039]

[0040] Table 2

[0041] For Figure 5 the Watt-Var curve shown, the segmented linear regions can be classified in a similar manner. Here, the X variable is the active power (P), and the Y variable is the reactive power (Q). Table 3 is from the IEEE 1547 code, which specifies the settings of the endpoints of the segmented regions, such as (P 1 , Q 1 ), (P 2 , Q 2 ), (P 3 , Q 3 ), (P 1 ’, Q 1 ’), (P 2 ’, Q 2 ’), and (P 3 ’, Q 3 ’).

[0042]

[0043] Table 3

[0044] The regulation curves on different national grid codes may have similar trends. Figure 6 shows the Volt-Var curve of the Italian CEI 0-16 code. Figure 7 shows the Volt-Var curve of the German VDE-AR 4110 code (the positive vertical axis represents the injection or under-excitation region; the negative vertical axis represents the absorption or over-excitation region). Compare Figure 4 , 6 7, it can be noted that the Volt-Var curves for the IEEE 1547 code, the CEI0-16 code, and the VDE-AR4110 code follow the same form. According to some embodiments, the values ​​of the parameters (X1, Y1), (X2, Y2), (X3, Y3), and (X4, Y4) defining the endpoints of the piecewise linear region can be updated to accommodate a given regulation curve for a given regional standard. Thus, the updated parameters can stretch, shrink, or shift the regulation curve to a new setting to compound a given code.

[0045] Even a complete characterization of a code may leave some parameters uninterpreted. For example, the IEEE 1547 code does not have a priority list on regulation curves, instead leaving it to the distribution system operator (DSO) to select a reactive power regulation curve and choose between a constant P or Volt-Watt real power curve. According to some embodiments, a case structure is deployed to select between a limited number of choices. The CEI grid code has a default priority list on regulation curves, although this may be changed as needed using priority coils, leaving the controller to determine which curves to follow.

[0046] According to some embodiments, the algorithm calculates the "p-word" and "q-word" based on priority. They are important tools for selecting which functions will provide power set points. The "q-word" is a priority data byte consisting of bit-by-bit binary elements or flags. For example: q-word:=q-const+2*q-pf+4*q-v+... Assign validity (MSB to LSB) to the curve based on the power priority flag. In this case, the Volt-Var flag qv is the MSB. When activated, the q-word>3 and Volt-Var is executed. When the q-word<1, the default set point is used. The "p-word" involves nested if loops, typically selecting between conflicting set points. For example, the Volt-Watt curve uses an optimal energy set point to track when the voltage is not high, but as V(PCC) approaches 1.1*Vpu, it shifts to absorb more power.

[0047] Parameterized ride-through timer

[0048] The term low voltage ride through (LVRT) (also known as under voltage ride through (UVRT) or fault ride through (FRT)) describes the minimum tolerance of electrical systems in a grid to short-term voltage drops. In the event of a voltage drop (also known as a voltage sag), the generator may not be immediately disconnected from the grid, but may continue to operate for a specific period of time. The term high voltage ride through (HVRT) refers to the handling of voltage increases or surges.

[0049] When the voltage or frequency exceeds the normal operating range, the state machine can enter a condition where, if the disturbance persists until the timer expires, the state machine will trip. According to some embodiments, for Figure 2 step 222 in, a technique is deployed to tabulate the (X, Y) thresholds of the crossing curve in a manner similar to the regulation curve. The crossing timer (Y threshold) may depend on the severity (X threshold) of the voltage (or frequency) disturbance, as discussed below.

[0050] Figure 8 Shows the low voltage ride through (LVRT) curve from the IEEE 1547 code. The vertical axis is the residual voltage (normalized). The horizontal axis is the minimum duration (referred to as the trip timer or crossing timer). Note that the LVRT curve has several step changes. The trip timer depends on the severity of the voltage drop under normal operating conditions. Table 4 from the IEEE 1547 code summarizes the trip timers under various conditions.

[0051]

[0052] Table 4

[0053] In Figure 8 , the shaded voltage band 810 between the values 0.88 and 1.00 is the normal operating voltage range. When the residual voltage is within the voltage band 810 (test conditions A and E in Table 4), the microgrid is in continuous operation mode. The shaded voltage band 820 between the values 0.00 and 0.05 is the momentary stop voltage range. When the voltage is between 0.00 and 0.05 (test condition B in Table 4), the microgrid is in momentary stop mode. When the voltage is between 0.00 and 0.50 (test condition C in Table 4), the trip timer is 10 seconds. When the voltage is between 0.52 and 0.70 (test condition C’ in Table 4), the trip timer is also 10 seconds. When the voltage is between 0.50 and 0.70 (test condition D in Table 4), the trip timer is 20 seconds. According to some embodiments, each step can be programmed with a unique timer independent of the timers in adjacent regions. For example, a deviation below 0.5 and lasting less than one second cannot reset the longer timer affected by the disturbance 0.50 < V < 0.88.

[0054] Fig. 9LVRT curves from the CEI0-16 code are shown. Note that the trip timer is linearly related to the voltage. According to some embodiments, this is achieved using a sliding timer, and the trip timer (duration) is inversely proportional to the voltage sag (i.e., the smaller the deviation from the normal operating voltage, the longer the trip timer). While the voltage remains in the crossing area, the timer can continuously adjust its holding time. According to some embodiments, the trip timer (duration of the voltage crossing) and the voltage threshold for entering and remaining in this state are parameterized according to a national grid code (e.g., IEEE 1547 code or CEI0-16 code) or user configuration.

[0055] Fig.10 An example of voltage ride-through according to the IEEE 1547 code is illustrated. Solid line 1002 is the grid voltage (normalized) plotted as a function of time. The voltage band indicated by vertical double arrow 1030 is the normal operating voltage range (e.g., between values ​​0.88 and 1.1). The voltage band indicated by vertical double arrow 1010 is the high voltage ride-through (HVRT) voltage range (e.g., between values ​​1.1 and 1.3). The voltage band indicated by vertical double arrow 1020 is the low voltage ride-through (LVRT) voltage range (e.g., between values ​​0.5 and 0.88). Horizontal arrow 1040 indicates the LVRT timer limit. In this example, because the measured PCC voltage remains within the LVRT voltage range for a duration below the LVRT timer limit, the system will not trip. With LVRT control, the voltage returns to the normal operating range. Horizontal arrow 1050 indicates the HVRT timer limit. Since the PCC voltage remains within the HVRT voltage range for a duration exceeding the HVRT timer limit, the microgrid circuit breaker at the PCC trips.

[0056] Below is an exemplary algorithm for setting the parameters of the LVRT trip timer. The algorithm can support various national grid codes. Similar to the regulation curve, each piecewise linear region of the voltage ride-through curve is bounded by endpoints. These endpoints can be captured by an array of V1, T1...Vn, Tn for code-specific trip time regions and Vpcc.

[0057]

[0058] Table 5 shows the settings of V1, T1...Vn, Tn for the UK code, the German code, the Italian code and the US code.

[0059]

[0060] Table 5

[0061] For IEEE 1547 code, the LVRT curve has a step size such as Figure 8As shown. Thus, the piecewise linear region includes horizontal and vertical sections. For example, the vertical section between endpoints 852 and 854 (in terms of the trip timer and voltage) can be defined by the parameters (V1, T1) and (V2, T2), where V1 = V2; the horizontal section between endpoints 854 and 856 can be defined by the parameters (V2, T2) and (V3, T3), where T2 = T3; the vertical section between endpoints 856 and 858 can be defined by the parameters (V3, T3) and (V4, T4), where V3 = V4; the horizontal section between endpoints 858 and 860 can be defined by the parameters (V4, T4) and (V5, T5), where T4 = T5.

[0062] For the CEI0 - 16 code, the LVRT curve includes a linear region defined by endpoints 930 and 940. This region is quite wide (e.g., in the voltage range of 0.15 < V < 0.85). It may require a fast response time at the low voltage end (e.g., trip timer ~ 200 ms). In the voltage range close to the normal range (e.g., 0.85 < V < 1.15), the trip timer is between 1.0 and 1.5 seconds.

[0063] If V1 = V2 or V2 = V3, the first condition to be solved is the vertical section. After this condition is solved in the first statement, the next statement in the code will consider the horizontal and linear regions as follows: (V - V2)*(T3 - T2) / (V3 - V2)+T2. This handles Figure 8 the horizontal section between endpoints 854 and 856 in Fig. 9 or the horizontal section between endpoints 920 and 930 in Fig. 9 and the linear section between endpoints 930 and 940 in

[0064] According to some embodiments, with a cycle time of 100 ms and a transmission delay of about another 100 ms, the trip timer can be calculated in the PLC and then passed as a trip timer parameter in the UV function to the relay. As long as the voltage is sampled and held for at least one cycle (100 to 150 ms), and the parameters T, uv are updated before the relay expires, this can ensure that the timer is faithfully executed.

[0065] The following is an exemplary algorithm.

[0066]

[0067] Parameterized Modbus communication

[0068] According to some embodiments, for Figure 2In step 230, for each DER, the IP address of the register is first decoded into a double word. The IP addresses can be ordered in chronological order, from the first register to the last register. The size of the required address space can be calculated as the length (NB) from the address of the first register to the address of the last register. Then, the message is crafted. In some embodiments, for each DER, the time to read consecutive messages can be incremented by 10 milliseconds (e.g., twice the PCC measurement rate at the circuit breaker). Each message can be active for a duration of 5ms. Any errors can be decoded into a string to check the packets on the network LAN.

[0069] Fig.11A and 11B Illustrated are sequential read messages (e.g., PV1, BESS1, BESS2) to multiple DERs 1110, 1120, and 1130 according to some embodiments. For example, the read message to DER 1110 is 150ms, the read message to DER 1120 is 160ms, and the read message to DER 1130 is 170ms, etc. Each read message is active within 5ms.

[0070] In order for the controller to comply with grid code requirements, meet energy management needs and communicate with the outside world, the controller requires various data from the DER as input. According to some embodiments, a set of function variables is defined based on the PCC function. Each function variable is assigned to a corresponding register of the DER so that the controller can locate the relevant input data.

[0071] According to some embodiments, Figure 2 In step 232 of the above, each DER is mapped to point to their Modbus register addresses from the function variables of the PCC function. Table 6 shows an example of Modbus mapping of a generic DER according to some embodiments. In order to correctly locate the data from each DER, a lookup table can be used to match the name and IP address of the register of each DER. The user can then connect the register of interest to the PCC function using the register address pointer available in the global variable.

[0072] According to some embodiments, all input data measured from the DER at the PCC are assigned to the data array data_read_grid. The parser can sort the data array data_read_grid to generate a smaller data array data_in_pcc, which only includes data related to function variables (such as voltage, current, frequency, etc.). Therefore, the data in the smaller data array data_in_pcc is a subset of the input data in the larger data array data_read_grid.

[0073] Below is an exemplary algorithm for the resolver. Each device within the control of the microgrid runs the for loop, starting with the PCC breaker and then moving to the storage device.

[0074]

[0075]

[0076] After the registers are mapped to function variables, an input array data_read_grid can be set up to read a large amount of data from each DER. The size of the read message can be determined by the length (NB) from the address of the first register to the address of the last register. The input array data_read_grid needs to be equal to or greater than the number of bytes read in the message. As described above, the parser can sort the large amount of data in the input array data_read_grid into a smaller data array data_in_pcc. According to some embodiments, the size of the address array is equal to the data array data_in_pcc, ensuring that each function variable is linked to an address pointer. All devices within the microgrid that meet a standard "category" (such as load, generation, or storage) can meet this condition.

[0077] Parameterized Aggregator

[0078] According to some embodiments, Figure 2 At step 234 in the microgrid, if there are any changes in the configuration of the microgrid (e.g., any DER has entered or left the microgrid, or the charge state of any DER has changed), the controller can update the aggregate PQ polygon characteristics and manage the power traffic on the bus accordingly. If a DER has entered or left the microgrid, the MB_PRG and subordinate functions can update the polling rate on the DER based on the number of active DERs in the loop (e.g., Fig.11A and 11B The controller may dynamically update its control loop and aggregate PQ boundaries as function parameters in the microgrid change, as discussed in more detail below.

[0079] Polling devices on the network

[0080] First, the controller defines all DERs in the microgrid and sets function parameters in global variables to address the minimum data array required for each DER according to its category. According to some embodiments, the process may include the following steps: (i) indicating the grid code and any category of DER, (ii) defining the nominal voltage and nominal frequency, (iii) providing the address of the input registers for each DER (e.g., according to Table 6), and (iv) determining the number of DERs of each category (e.g., load, PV, BESS) in the microgrid. According to some embodiments, the microgrid may include up to 30 loads, 3 PVs, 3 BESSs, and 1 circuit breaker. The addresses of the following holding registers in the Modbus map may be specified: trip coils at the PCC (e.g., circuit breakers), PQ setpoints for all BESSs, and load coils in the case of demand response. The input registers are found in Table 6.

[0081]

[0082]

[0083] Table 6

[0084] In some embodiments, the controller's communication channel can check incoming data from the DER to verify that the register address is set correctly. If an invalid register address is found, the DER can be disabled. Disabling or changing any DER within the microgrid may trigger reinitialization. Reshaping the microgrid size by the number of valid devices is performed by the slave PLC function "Read Maps." The evolution of the microgrid as the controllable devices change over time is reported to the PQ polygon. The controller can use the updated DER conditions to define the aggregation boundary on the microgrid as the sum of the power available in the individual DERs, as described in more detail below. The general data structure provided in accordance with the embodiments of the present disclosure enables overall simplicity.

[0085] As the microgrid evolves, all classes of devices (e.g., generation, storage, and loads) can continually reshape the PQ polygon. According to some embodiments, when a new device is activated, the controller first parses the Modbus mapping of all its registers into the data required to conform to the data type of the device class. If the new DER is approved, the controller can add the rated power of the new DER to the PCC aggregate and can poll it in the next DER time slot (e.g., Fig.11A and 11B Conversely, if a new DER is found to not meet the requirements, the controller can remove the rated power of the new DER from the PCC aggregation and reduce the polling rate of the new DER by a factor of 100. This can free up DER time slots on the message queue to poll other devices and optimize throughput.

[0086] Shaping PQ polygons

[0087] The controller reads data from the DERs in the microgrid, runs the PCC function and calculates the output from the aggregated P&Q proportional-integral (PI) controller (e.g., Figure 2 After execution of the EMSM 226 in the EMSM 226, the setpoints are distributed to the dispatchable generation or (charging) storage units. The controller can determine which storage units to charge based on the state of charge (SOC), which may affect the aggregate PQ polygon.

[0088] According to some embodiments, the power distribution provided by the storage cells is determined according to the fractional state of charge (SOC) of each storage cell relative to the total SOC accumulated in all storage cells. The fractional SOC of the storage cell BESS(n) may be defined as:

[0089]

[0090] Among them, SOC bess(n) is the SOC of the storage unit BESS(n), and the total SOC bess(1...n) is the total SOC of all storage units in the microgrid.

[0091] According to some embodiments, the controller can dynamically classify each storage unit in the microgrid as "generation only" (gen), "balancing" or "absorption only" (abs) based on the fractional SOC of each storage unit. For example, if the fractional SOC of a storage unit is greater than a first threshold (e.g., 80%), the storage unit can be classified as "generation only"; if the fractional SOC is less than a second threshold (e.g., 20%), the storage unit can be classified as "absorption only"; if the fractional SOC is between the first threshold and the second threshold, the storage unit can be classified as "balancing". Those units characterized as generation only or balancing can be considered to be charging. Units characterized as absorption only can be considered to be charging. After classifying each storage unit, the total controllable power available to the PCC in each direction (generation and absorption, respectively) can be evaluated:

[0092]

[0093]

[0094] Among them, P pcc(gen) is the total active power generated at the PCC (maximum magnitude positive active power), P pcc(abs) is the total active power available for absorption at the PCC (negative active power of maximum magnitude), and P pcc(nom) is the nominal power at the PCC. Fig.12 As shown in the figure, P pcc(gen) and P pcc(abs) The value of can set the boundary of the PQ polygon.

[0095] According to some embodiments, power deaggregation of the individual storage units (distribution of active power provided by the individual storage units) is configured as follows:

[0096]

[0097] Where P bess(n) is the power set point of the storage unit BESS(n).

[0098] When absorbing power from the PCC, the inverse of the SOC can be used to determine which storage cells are best suited for power storage (charging). For example, the storage cells with the lowest charge can be designated for power storage. According to some embodiments, if true power is to be absorbed at the PCC, the controller uses the parameter bess[n]true_soc, defined as follows:

[0099] If PCC Pref>0Then

[0100] BESS1_true_soc:=data_in_bess1[soc];

[0101] ELSIF PCC Pref<0 Then

[0102] BESS1_true_soc:=100-data_in_bess1[soc].

[0103] The deaggregation of the power absorbed by the individual storage cells is set as follows:

[0104]

[0105] Where P bess(n) is the power set point of the storage unit BESS(n).

[0106] Fig.1313 is a flow chart illustrating a method of operating a microgrid controller according to some embodiments. The method includes obtaining a set of parameter data representing one or more regulation curves of one or more national grid codes in 1310. The one or more regulation curves are associated with a set of function variables of a point of common coupling (PCC) function executed by the controller. The method also includes configuring a message to a plurality of distributed energy resources (DERs) interconnected to the PCC in 1320. The message is configured to read input data from a register of each DER. The method also includes executing a PCC function to control the microgrid according to at least one of the one or more regulation curves based on a subset of the input data from each DER associated with the set of function variables in 1330.

[0107] According to some embodiments, the method further includes obtaining a register map for each corresponding DER, the register map linking a subset of registers of the corresponding DER to a set of function variables, and parsing the input data using the register map to obtain the subset of input data. Each DER in the plurality of DERs may be classified as one of a load, a source, or a store.

[0108] According to some embodiments, each corresponding regulation curve specifies a relationship between two function variables in a set of function variables. Each corresponding regulation curve includes a piecewise linear region defined by a plurality of endpoints. The parameter data set may include the coordinates of the plurality of endpoints defining the piecewise linear region. One or more national grid codes may be selected from a predefined national grid code library. The predefined national grid code library may include, for example, an IEEE 1547 code, a CEI0-16 code, or a VDEAR4110 code. In some embodiments, a parameter data set of one or more regulation curves characterizing one or more national grid codes may be preloaded in a controller.

[0109] Fig.14 1 is a simplified block diagram of a controller 1400 for controlling a microgrid according to some embodiments. The controller 1400 includes a computer memory 1410 and one or more computer processors 1420. The computer memory 1410 may be configured to store a set of parameter data representing one or more regulation curves of one or more national grid codes. The one or more regulation curves are associated with a set of function variables of a PCC function. The one or more computer processors may be configured to send a message to a plurality of DERs to read input data from registers of each DER, and based on a subset of the input data from each DER associated with the set of function variables, execute the PCC function according to at least one of the one or more regulation curves to control the microgrid.

[0110] The controller 1400 may also include a user interface 1430. For example, the user interface 1430 may allow a user to enter parameter data characterizing additional regulation curves for additional national grid codes, which parameter data may be stored in the computer memory 1410. The controller 1400 may also include a communication device 1440. For example, the communication device 1440 may include a wired and / or wireless communication device for communicating with a DER or the outside world.

[0111] As described above, embodiments of the present disclosure provide a method for initializing a low voltage AC microgrid controller that can be easily adapted to comply with various national grid codes and read relevant data from various DERs. The microgrid controller can dynamically reshape the aggregation boundaries of the PCC control loop as DERs enter and leave the microgrid. Embodiments of the present disclosure can provide robust control at the PCC while allowing organic DER growth at industrial sites.

[0112] Although the subject matter of the present disclosure has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description should be considered illustrative or exemplary, rather than restrictive. Since the invention is defined by the claims, any statement characterizing the invention herein should also be considered illustrative or exemplary, rather than restrictive. It is to be understood that changes and modifications may be made by one of ordinary skill in the art within the scope of the following claims, which may include any combination of features from the different embodiments described above.

[0113] The terms used in the claims should be interpreted as having the broadest reasonable interpretation consistent with the preceding description. For example, the use of the article "a" or "the" when introducing an element should not be interpreted as excluding multiple elements. Similarly, the statement of "or" should be interpreted as inclusive, so that the statement of "A or B" does not exclude "A and B", unless it is obvious from the context or the preceding description that only one of A and B is intended. Further, the statement of "at least one of A, B and C" should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories. Moreover, the statement of "A, B and / or C" or "at least one of A, B or C" should be interpreted as including any single entity from the listed elements (e.g., A), any subset from the listed elements (e.g., A and B), or the entire list of elements A, B and C.

Claims

1. A method for operating a controller of a microgrid, the method comprising: obtaining a set of parameter data representing one or more regulation curves of one or more national grid codes, the one or more regulation curves being associated with a set of function variables of a point of common coupling (PCC) function executed by the controller; configuring a message to a plurality of distributed energy resources DERs interconnected to the PCC, the message being used to read input data from a register of each DER; as well as Based on a subset of the input data from each DER associated with the set of function variables, the PCC function is executed to control the microgrid according to at least one of the one or more regulation curves.

2. The method according to claim 1, further comprising: obtaining a register map for each corresponding DER, the register map linking a subset of the registers of the corresponding DER to the set of function variables; as well as The input data from the corresponding DER is parsed using the register map to obtain the subset of the input data.

3. The method of claim 2, wherein each DER of the plurality of DERs is classified as one of a load, a source, or a storage.

4. The method of claim 1 , wherein each respective tuning curve specifies a relationship between two function variables in the set of function variables, and each respective tuning curve comprises a piecewise linear region bounded by a plurality of endpoints, and wherein the parameter data set comprises coordinates of the plurality of endpoints that bound the piecewise linear region.

5. The method according to claim 4, wherein the one or more regulation curves include one or more of a reactive power relative to voltage curve (Volt-Var), a reactive power relative to active power curve (Watt-Var), a reactive power relative to power factor curve (PF-Var), an active power relative to voltage curve (Volt-Watt), a low voltage ride through (LVRT) curve, a high voltage ride through (HVRT) curve, or a frequency drop curve. The method of claim 1 , wherein the one or more national grid codes are selected from a predefined national grid code library. 7 . The method according to claim 6 , wherein the predefined national grid code library comprises one or more of IEEE 1547 code, CEI0-16 code or VDE AR4110 code.

8. The method of claim 6, wherein the one or more national grid codes include two or more different national grid codes, wherein the one or more regulation curves include multiple regulation curves of the two or more different national grid codes, and wherein the parameter data set characterizing the multiple regulation curves has a common data format between the different national grid codes.

9. The method of claim 1, wherein the set of parameter data characterizing the one or more regulation curves of the one or more national grid codes is preloaded in the controller.

10. The method according to claim 1, further comprising: receiving, from a user, additional parameter data characterizing one or more additional regulation curves for one or more additional national grid codes; as well as The additional parameter data is stored in the controller.

11. The method according to claim 1, further comprising: Aggregate active power is allocated among the plurality of DERs based on a fractional state of charge (SOC) of each DER relative to a total state of charge (SOC) accumulated among the plurality of DERs.

12. The method according to claim 11, further comprising: The allocation of aggregate active power is updated upon detecting one of: (i) a new DER enters the microgrid, (ii) an existing DER leaves the microgrid, or (iii) a change occurs in any of the plurality of DERs.

13. A controller for controlling a microgrid, the microgrid comprising a plurality of distributed energy resources DER, the plurality of distributed energy resources DER being interconnected to a common coupling point PCC, the controller comprising: a memory configured to store a set of parameter data representing one or more regulation curves of one or more national grid codes, the one or more regulation curves being associated with a set of function variables of a PCC function; as well as One or more processors, configured to sending a message to the plurality of DERs to read input data from a register of each DER; as well as Based on a subset of the input data from each DER associated with the set of function variables, the PCC function is executed to control the microgrid according to at least one of the one or more regulation curves.

14. The controller according to claim 13, wherein: The memory is further configured to store a register map for each corresponding DER, the register map linking a subset of the registers of the corresponding DER to the set of function variables; and The one or more processors are further configured to parse the input data from a corresponding DER using the register map to obtain the subset of the input data.

15. The controller of claim 13 , wherein each respective tuning curve specifies a relationship between two function variables in the set of function variables, and each respective tuning curve comprises a piecewise linear region bounded by a plurality of endpoints, and wherein the parameter data set comprises coordinates of the plurality of endpoints that bound the piecewise linear region.

16. The controller of claim 13, wherein the one or more National Grid codes are selected from a predefined National Grid code library.

17. A controller according to claim 13, wherein the one or more national grid codes include two or more different national grid codes, wherein the one or more regulation curves include multiple regulation curves of the two or more different national grid codes, and wherein the parameter data set characterizing the multiple regulation curves has a common data format between the two or more different national grid codes.

18. A non-transitory computer readable medium having stored thereon instructions which, when executed by one or more hardware processors, cause execution of a method for operating a controller of a microgrid, the method comprising: obtaining a set of parameter data representing one or more regulation curves of one or more national grid codes, the one or more regulation curves being associated with a set of function variables of a point of common coupling (PCC) function executed by the controller; configuring a message to a plurality of distributed energy resources DERs interconnected to the PCC, the message being used to read input data from a register of each DER; as well as Based on a subset of the input data from each DER associated with the set of function variables, the PCC function is executed to control the microgrid according to at least one of the one or more regulation curves.

19. The non-transitory computer-readable medium of claim 18, wherein each respective tuning curve specifies a relationship between two function variables in the set of function variables, and each respective tuning curve comprises a piecewise linear region bounded by a plurality of endpoints, and wherein the parameter data set comprises coordinates of the plurality of endpoints that bound the piecewise linear region.

20. The non-transitory computer-readable medium of claim 18, wherein the one or more national grid codes comprise two or more different national grid codes, wherein the one or more regulation curves comprise multiple regulation curves of the two or more different national grid codes, and wherein the parameter data sets characterizing the multiple regulation curves have a common data format between the two or more different national grid codes.

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