Secondary control of energy supplies in DC and hybrid microgrids

Abstract

Direct current (DC) microgrids and hybrid microgrids require a controller for both voltage control and load sharing. The disclosed embodiments can simultaneously calculate values for both voltage control and load sharing without communicating between energy supplies, and incorporate these values into a single setpoint. This enables setpoint determination to be included in a single controller, which may be provided as a secondary controller, which may provide the determined setpoint to the primary controller of each DC / DC converter of each energy supply.

Description

TECHNICAL FIELD

[0001] Embodiments described herein relate generally to control of energy supplies, and more particularly, to secondary control of energy supplies, such as battery energy storage systems, in direct current (DC) and hybrid microgrids. BACKGROUND

[0002] In the past, direct current (DC) microgrids were typically small systems, often in the range of tens of kilowatts (kW) in size. However, there has been a significant increase in the deployment of distributed energy resources with DC output. Additionally, energy storage systems typically have an internal DC bus, and modern electronic loads often require DC power. As a result, DC microgrids and hybrid microgrids with both alternating current (AC) and DC buses have become increasingly popular.

[0003] The use of distributed energy supplies, such as battery energy storage systems (BESS) and other constant power generators, in DC or hybrid microgrids requires controllers for both voltage control and load sharing. As the size of microgrids increases, more comprehensive control structures are needed. The present disclosure addresses this need and other problems discovered by the inventors. SUMMARY

[0004] One goal of certain disclosed embodiments is to provide both voltage control and load sharing using a single setpoint. As an additional goal, the disclosed embodiments can implement voltage control and load sharing in a secondary controller that provides a setpoint to a primary controller. As yet another goal, secondary controllers for different energy supplies can operate independently of one another.

[0005] In an embodiment, a method of controlling an energy supply includes using a controller of the energy supply to: determine a voltage control value based on a first error between a reference parameter of a bus to which the energy supply is electrically connected and a measured parameter of the bus; determine a load sharing value based on a second error between a reference power of the energy supply and a measured power output by the energy supply; determine a setpoint based on the voltage control value and the load sharing value; and output the setpoint to control one or both of a voltage of the bus and the power output by the energy supply according to the setpoint. The setpoint can be a voltage setpoint. The setpoint can be determined as a sum of the voltage control value and the load sharing value.

[0006] The voltage control value can be a first voltage value, the reference parameter can be a reference voltage of the bus, and the measured parameter can be a measured voltage at the bus. The method can further include using the at least one controller to calculate a first error based on a difference between the reference voltage and the measured voltage. The first error can be further calculated based on an estimated voltage drop on an electrical line between the bus and the energy supply. The method can further include using the controller to estimate the voltage drop based on an estimated resistance on the electrical line and a current output by the energy supply.

[0007] The load sharing value can be a second voltage value, and the method can further include using the controller to convert the second error from a power value to a voltage value. The method can further include using the controller to calculate the second error based on a difference between the reference power and the measured power. The second error can be further calculated based on an estimated power loss on an electrical line between the bus and the energy supply. The second error can be converted from a power value to a voltage value based on a droop coefficient associated with a direct current (DC) / DC converter of the energy supply.

[0008] The load sharing value can be further a second voltage value, and the method can further include using the controller to convert the second error from a power value to a voltage value, using the controller to calculate the second error based on a difference between the reference power and the measured power, and the second error can be further calculated based on an estimated power loss on an electrical line between the bus and the energy supply.

[0009] The method can further include using the controller to calculate the reference power as a proportion of a total load based on a nominal power of the energy supply relative to nominal powers of one or more other energy supplies. The energy supply can be a battery energy storage system or a power generator. The controller can be a secondary controller, where the setpoint is output by the secondary controller to an input of a primary controller of the energy supply, and the method can further include using the primary controller to control one or both of a voltage of the bus and a power output by the energy supply based on the setpoint output by the secondary controller. The secondary controller can output the setpoint to a voltage control module of the primary controller.

[0010] In an embodiment, a controller for an energy supply is configured to determine a voltage control value based on a first error between a reference parameter of a bus to which the energy supply is electrically connected and a measured parameter of the bus, determine a load sharing value based on a second error between a reference power of the energy supply and a measured power output by the energy supply, determine a setpoint based on the voltage control value and the load sharing value, and output the setpoint to control one or both of a voltage of the bus and a power output by the energy supply according to the setpoint. The controller can be a secondary controller configured to output the setpoint to a voltage control module of a primary controller in a direct current (DC) / DC converter of the energy supply. The energy supply can be a battery energy storage system or a power generator within a microgrid. The voltage control value can be a first voltage value, the reference parameter can be a reference voltage of the bus, and the measured parameter can be a measured voltage at the bus. The first error can be calculated as a difference between the reference voltage and an estimated voltage drop on an electrical line between the bus and the energy supply and a sum of two. The load sharing value can be a second voltage value. The second error can be calculated as a difference between the measured power and an estimated power loss on the electrical line and a sum of two. The controller can be further configured to convert the second error from a power value to a voltage value.

[0011] The load sharing value can further be a second voltage value, and the controller can be further configured to convert the second error from a power value to a voltage value, calculate the second error based on a difference between the reference power and the measured power, and further calculate the second error based on an estimated power loss on an electrical line between the bus and the energy supply.

[0012] It should be understood that any of the features described above can be implemented alone or in any combination with any subset of other features. Accordingly, to the extent that the appended claims suggest particular dependencies among features, the disclosed embodiments are not limited to those particular dependencies. Rather, any of the features described herein can be combined with any other feature described herein, or implemented in any combination of features, whether or not described herein. In addition, any of the methods described above and elsewhere herein can be embodied in software and / or hardware in one or more controllers. BRIEF DESCRIPTION OF DRAWINGS

[0013] The details of the application, both as to its structure and operation, can be gleaned in part by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which:

[0014] Figure 1 a single line diagram of a hybrid microgrid is illustrated in accordance with an example;

[0015] Figure 2 Figures illustrate processes for controlling energy supplies according to embodiments;

[0016] Figure 3 Figures illustrate primary and secondary controllers according to embodiments;

[0017] Figure 4 Figures illustrate examples of processing devices that can be used as or in controllers according to embodiments;

[0018] Figure 5 Figures illustrate single line diagrams according to simulation examples showing sudden load changes in a microgrid during islanded conditions;

[0019] Figure 6A and Figure 6B Figures illustrate power and voltage curves achieved by embodiments in simulation examples; and

[0020] Figure 7 Figures illustrate load sharing between two battery energy storage systems achieved by embodiments in simulation examples. DETAILED DESCRIPTION

[0021] In embodiments, systems and methods for secondary control of energy supplies, such as battery energy storage systems (BESS), within a DC or hybrid microgrid are disclosed. After reading this description it will become apparent to a person skilled in the art how to implement the application in various alternative embodiments and alternative applications. However, although various embodiments of the application will be described herein, it is understood that these embodiments are presented by way of example only and not limitation, as the application can be embodied in a wide variety of configurations and modifications. Thus, this detailed description should not be interpreted as a limitation on the scope or breadth of the application as set forth in the appended claims.

[0022] Figure 1A single line diagram of a hybrid microgrid is illustrated in accordance with an example. The hybrid microgrid 100 includes a point of common coupling 110, e.g., between a utility grid (not shown) and a distribution network of the hybrid microgrid 100, which can include one or more AC microgrids 120 and one or more DC microgrids 130. A transformer 115 can be positioned in front of or behind the point of common coupling 110 to transform power from a high voltage used by the distribution network of the utility grid to a low voltage used by the hybrid microgrid 100. Although two AC microgrids 120A and 120B and two DC microgrids 130A and 130B are illustrated in a particular arrangement, the hybrid microgrid 100 can include any number of AC microgrids (e.g., one, three, four, etc.) and any number of DC microgrids (e.g., one, three, four, etc.) in any arrangement. Additionally, it should be understood that the disclosed embodiments can be equally readily applied to a single DC microgrid 130 or a collection of multiple DC microgrids 130 rather than the hybrid microgrid 100.

[0023] The hybrid microgrid 100 can include circuit breakers 140 at one or more points within the distribution network. Thus, individual portions of the distribution network can be isolated by tripping the circuit breaker(s) 140. For example, the AC microgrid 120A includes a circuit breaker 140A between its distribution network and the point of common coupling 110, and the AC microgrid 120B includes a circuit breaker 140B between its distribution network and the point of common coupling 110. Additionally, the DC microgrid 130A includes a circuit breaker 140C between a pair of DC buses, and the DC microgrid 130B includes a circuit breaker 140D between a pair of DC buses.

[0024] Each of the AC microgrids 120 and DC microgrids 130 can serve one or more loads 150, including critical loads and / or auxiliary loads. For example, the AC microgrid 120A serves loads 150A and 150B on an AC bus, the AC microgrid 120B serves loads 150C and 150D on an AC bus, the DC microgrid 130A serves a load 150E on a DC bus, and the DC microgrid 130B serves a load 150F on a DC bus.

[0025] AC / DC converters 160 can be disposed at the coupling points between the AC microgrids 120 and the DC microgrids 130 to convert AC power from the AC microgrids 120 to DC power in the DC microgrids 130 and vice versa. For example, AC / DC converter 160A is disposed between the AC bus of AC microgrid 120A and the DC bus of DC microgrid 130A, and AC / DC converter 160B is disposed between the AC bus of AC microgrid 120B and the DC bus of DC microgrid 130B.

[0026] The DC microgrids 130 can include DC / DC converters or solid-state transformers 170 between DC buses at different voltages. For example, DC microgrid 130A includes solid-state transformer 170A between a pair of DC buses, and DC microgrid 130B includes solid-state transformer 170B between a pair of DC buses.

[0027] The hybrid microgrid 100 can include one or more constant energy supplies 180. The constant energy supplies 180 can include, but are not limited to, battery energy storage systems (BESS), power generators, or any other components capable of supplying constant power to the electrical distribution network. Typically, each energy supply 180 will output DC power. For energy supplies 180 that output DC power to a DC bus, a DC / DC converter 182 can be disposed between the energy supply 180 and the DC bus to regulate the voltage on the DC bus. For example, energy supply 180A outputs DC power to DC / DC converter 182A in DC microgrid 130A, and energy supply 180C outputs DC power to DC / DC converter 182C in DC microgrid 130B. For energy supplies 180 that output DC power to an AC bus, an AC / DC converter 184 can be disposed between the energy supply 180 and the AC bus to convert the DC power output by the energy supply 180 to AC power. For example, energy supply 180B outputs DC power to AC / DC converter 184B in AC microgrid 120B.

[0028] The hybrid microgrid 100 can also include one or more non-constant energy supplies 190, which can be renewable energy dependent power generators. The non-constant energy supplies 190 can include, but are not limited to, wind (e.g., generated by a wind turbine), solar (e.g., generated by a photovoltaic cell), wave (e.g., generated by a wave energy converter), or any other component that has the ability to supply current to the power distribution network that is dependent on a varying and non-constant source of energy. For example, energy supply 190A can be a wind power generator that outputs AC power to an AC / DC converter 184A in the DC microgrid 130B, and energy supply 190B can be a solar power generator that outputs DC power to a DC / DC converter 182B in the DC microgrid 130B.

[0029] Again, it should be understood that the hybrid microgrid 100 as illustrated in FIG. 1 is one non-limiting example. In practice, the hybrid microgrid 100 can include any number and arrangement of AC microgrids 120, DC microgrids 130, circuit breakers 140, loads 150, AC / DC converters 160, DC / DC converters or solid state transformers 170, constant energy supplies 180, and non-constant energy supplies 190. It should also be understood that any energy supply 180 or 190 can output power to a DC / DC converter 182, an AC / DC converter 184, or an AC / AC converter (not shown), depending on whether it outputs AC or DC power and whether it outputs power to an AC or DC bus. Of particular relevance to the present disclosure is that the DC / DC converter 182 at the output of a constant energy supply 180 can be controlled by a controller to regulate the voltage and / or power on the DC bus. Figure 1

[0030] Figure 2 A process 200 for controlling an energy supply 180 is illustrated in accordance with an embodiment. The process 200 can be implemented as software, hardware, or a combination of software and hardware in a controller of a DC / DC converter 182 that regulates the voltage and / or power of an energy supply 180 that outputs DC power. The process 200 can be used to determine a setpoint for controlling the voltage of a bus to which the energy supply 180 provides power and / or for controlling the power output by the energy supply 180. The process 200 can be performed repeatedly and iteratively as long as the DC / DC converter 182 is under control to continuously adjust the setpoint in real-time. It should be understood that these continuous real-time executions of the process 200 can be performed by each controller of each DC / DC converter 182 that regulates the power output by an energy supply 180 independently of the controllers of other DC / DC converters 182 that regulate the power output by other energy supplies 180.

[0031] ​Although process 200 is illustrated as having certain arrangements and ordering of sub-processes, process 200 can be implemented with fewer, more, or different sub-processes, and in different arrangements and / or ordering of sub-processes. Additionally, it should be understood that any sub-process that does not depend on the completion of another sub-process can be performed before, after, or in parallel with other independent sub-processes, even if these sub-processes are described or illustrated in a particular order.

[0032] In sub-process 210, a voltage control value is determined. In an embodiment, the voltage control value is determined based on a first error between a reference parameter of a bus to which energy supply 180 is electrically connected and a measured parameter of the bus. The reference parameter can be a reference voltage of the bus, and the measured parameter can be a measured voltage of the bus, such that the voltage control value is a first voltage value. For example, the voltage control value can be calculated as:

[0033] Equation (1):

[0034] V1= (K p1 V err1 + K I1 ∫V err1 )

[0035] where V1is the voltage control value, V err1 is the first error, K p1 is a first proportional gain for proportional control in a first proportional-integral (PI) controller of DC / DC converter 182, and K I1 is a first integral gain for integral control in the first PI controller of DC / DC converter 182. Gains K p1 and K I1 may be constants determined in any known manner for the first PI controller.

[0036] In an embodiment, the first error V err1 may be calculated based on a difference between the reference voltage and the measured voltage of the bus. Additionally, the first error V err1 may be calculated based on an estimated voltage drop on an electrical line between the bus and energy supply 180. For example, the first error V err1 may be calculated as:

[0037] Equation (2):

[0038] V err1 = V ref + V line_drop -V meas

[0039] where V ref is the reference voltage of the bus, V line_dropV is an estimated voltage drop on the electrical wire between the bus and the energy supply 180, and V meas is a measured voltage at the bus.

[0040] The voltage drop V line_drop may be estimated in any known manner. For example, if the resistance on the electrical wire is estimated or known, the voltage drop V line_drop may be estimated as the estimated resistance on the electrical wire multiplied by the current output by the energy supply 180. Adding the voltage drop V line_drop to the reference voltage V ref during the calculation of the first error can result in improved voltage control.

[0041] In sub-process 220, a load sharing value is determined. In an embodiment, the load sharing value is determined based on a second error between a reference power of the energy supply 180 and a measured power output by the energy supply 180. The load sharing value can be a second voltage value. For example, the load sharing value can be calculated as:

[0042] Equation (3):

[0043] V2 = (K p2 V err2 + K I2 ∫V err2 )

[0044] where V2 is the load sharing value, V err2 is the second error, K p2 is a second proportional gain for proportional control in the second PI controller for the DC / DC converter 182, and K I2 is a second integral gain for integral control in the second PI controller for the DC / DC converter 182. The gains K p2 and K I2 may be constants determined in any known manner for the second PI controller.

[0045] In an embodiment, the second error V err2 may be calculated based on a difference between the reference power and the measured power output by the energy supply 180. Additionally, the second error V err2 may be calculated based on an estimated power loss on the electrical wire between the bus and the energy supply 180. For example, the second error V err2 may be calculated as:

[0046] Equation (4): V err2 = P2V*P err

[0047] Equation (5):

[0048]

[0049] Equation (6):

[0050] P err = P ref + P line_loss - P meas

[0051] where AV max is the maximum allowed voltage deviation, P nom is the nominal power capacity of the energy supply 180, P ref is the reference power, P line_loss is the estimated power loss on the electrical wires between the bus and the energy supply 180, and P meas is the measured power output by the energy supply 180.

[0052] Notably, P2V represents a droop coefficient associated with the controller of the DC / DC converter 182. It is assumed that the control of the energy supply 180 is based on voltage droop (i.e., a terminal voltage drop proportional to the load on the energy supply 180). P err represents the error between the reference power and the measured power while taking into account the estimated power loss. The droop coefficient P2V converts the error P err (which is a power value) into a second error V err2 (which is a voltage value).

[0053] The power loss P line_loss may be estimated in any known manner. For example, if the resistance on the electrical wires is estimated or known, the power loss P line_loss may be estimated based on the estimated resistance on the electrical wires and the current output by the energy supply 180. During the calculation of the second error, the power loss P line_loss is added to the reference power P ref to compensate for the power loss P line_loss experienced between the bus and the energy supply 180 with the amount of power delivered to the bus.

[0054] The reference power P ref for a given energy supply 180 can be calculated as:

[0055] Equation (7):

[0056]

[0057] where n is the total number of energy supplies 180 outputting power to the bus, such that represents the sum of the nominal power capacities of all energy supplies 180 outputting power to the bus, and P loadis the total load to be injected into the bus by all energy supplies 180 that output power to the bus.

[0058] Notably, P ref represents the total load P load based on the nominal power capacity of the energy supply 180 connected to the controlled DC / DC converter 182 relative to all available energy supplies 180 that should be taken up by that energy supply 180. In other words, the reference power P ref is calculated as a certain proportion of the total load, all energy supplies including the energy supply 180 and potentially one or more other energy supplies 180. Thus, the reference power P ref load sharing is incorporated into the setpoint determination for each individual energy supply 180.

[0059] In sub-process 230, a setpoint is determined based on the voltage control value determined in sub-process 210 (e.g., Vi) and the load sharing value determined in sub-process 220 (e.g., V2). It should be understood that sub-processes 210 and 220 can be performed in parallel, as one sub-process does not necessarily depend on the other. In embodiments, the setpoint can be calculated as the sum of the voltage control value Vi and the load sharing value V2:

[0060] Equation (8): V set = Vi + V2

[0061] where V set is the setpoint. Notably, the setpoint V set combines both voltage control as implemented by the voltage control value Vi and load sharing as implemented by the load sharing value V2 into a single setpoint value. In embodiments, both the voltage control value Vi and the load sharing value V2 are voltage values, such that the setpoint V set is also a voltage value.

[0062] In sub-process 240, the setpoint determined in sub-process 230 (e.g., V set ) is output to control one or both of the voltage of the bus and the power output by the energy supply 180 according to the setpoint. In embodiments, process 200 is performed by a secondary controller, in which case the setpoint can be output by the secondary controller to an input of a primary controller of the energy supply 180. For example, the setpoint can be input to a voltage control module of the primary controller. The primary controller can then control the voltage output by the energy supply 180 to the bus based on the setpoint output by the secondary controller.

[0063] Figure 3Primary controller 310 and secondary controller 320 are illustrated in accordance with an embodiment. Primary controller 310 and / or secondary controller 320 can be implemented as software, hardware, or a combination of software and hardware, with some functions performed by software and other functions performed by hardware. In embodiments in which one or more of the described functions are performed by software, the software instructions and / or other data can be loaded into a main memory from a storage device and executed by one or more hardware processors. In embodiments in which one or more of the described functions are performed by hardware, the functions can be implemented as special-purpose processors, integrated circuits (ICs), application-specific integrated circuits (ASICs), digital signal processors (DSPs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gates or transistor logic, and / or the like.

[0064] For clarity of understanding, various components are described in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. In addition, the grouping of functions within a component is for ease of description. Specific functions can be moved from one component to another without departing from the scope of the present disclosure.

[0065] Secondary controller 320 can maintain reference parameter 322, for example, in persistent memory. Reference parameter 322 can be a constant value, such as a reference voltage V ref for the bus. In addition, secondary controller 320 can include a voltage drop estimation unit 324 that estimates voltage drop V line_drop based on, for example, an estimated resistance on the electrical line and a measured current (e.g., local current measurement 348). The reference parameter 322 is summed with the voltage drop V line_drop estimated by voltage drop estimation unit 324 by adder 326. It is understood that adder 326 corresponds to V ref+ V line_drop as performed in sub-process 210.

[0066] Secondary controller 320 can receive local voltage measurement 328 as an input. Local voltage measurement 328 corresponds to measured voltage V meas Local voltage measurement 328 is subtracted from the output of adder 326 by subtractor 330. It is understood that subtractor 330 corresponds to -V meas as performed in sub-process 210. Thus, the output of subtractor 330 is first error V err1 .

[0067] The secondary controller 320 may include a first PI controller 334, which receives a first error V from the subtractor 330. err1 As input, the first PI controller 334 can store or otherwise derive the gain K. p1 and K I1 The value of K. The first PI controller 334 can adjust the gain K. p1 and K I1 With the first error V err1 The voltage control value V1 is calculated according to formula (1), as performed in subprocess 210. The first PI controller 334 outputs the calculated voltage control value V1 to adder 360.

[0068] The secondary controller 320 may include a reference power P calculation module. ref The reference power calculation unit 342 can store or otherwise derive the nominal power capacity P of all available energy supply units 180. nom The value or nominal power capacity of the controlled energy supply unit 180 is the nominal power ratio to the total nominal power capacity of all available energy supply units 180. The secondary controller can receive a total load of 343 (representing P). load The reference power calculation unit 342 can use the total load 343 and the nominal power capacity P as input. nom Alternatively, the nominal power ratio can be used in conjunction with formula (7) to calculate the reference power P. ref As executed in subprocess 220.

[0069] The secondary controller 320 may include a power loss estimation unit 344, which estimates power loss, for example, based on an estimated resistance on the wire and a measured current (e.g., a local current measurement 348). The reference power P calculated by the reference power calculation unit 342 is then amplified by adder 346. ref The power loss P estimated by the power loss estimation unit 344 line_loss Perform the summation. It should be understood that adder 346 corresponds to P in formula (6). ref +P line_loss As executed in subprocess 220.

[0070] The secondary controller 320 can receive a local current measurement value 348 as input. The secondary controller 320 may include a power-to-measure calculation unit 349, which calculates the power-to-measure P based on the local voltage measurement value 328 and the local current measurement value 348. meas (For example, calculated as the product of local voltage measurement 328 and local current measurement 348). The measured power P calculated by the measured power calculation unit 349 is subtracted from the output of adder 346 by subtractor 350.meas It is understood that subtractor 350 corresponds to -P in equation (6) as performed in sub-process 220. meas The output of subtractor 350 is the power error P err .

[0071] Secondary controller 320 can include a power-to-voltage converter 352. Power-to-voltage converter 352 converts the power error P err output by subtractor 350 into a second error V err2 . In particular, power-to-voltage converter 352 can multiply the power error P err by a downward scaling factor. It is understood that power-to-voltage converter 352 corresponds to equations (4) and (5) as performed in sub-process 220.

[0072] Secondary controller 320 can include a second PI controller 354 that receives the second error V err2 as input from power-to-voltage converter 352. Second PI controller 354 can store or otherwise derive values for gains K p2 and K I2 . Second PI controller 354 can utilize gains K p2 and K I2 in combination with the second error V err2 to calculate a load sharing value V2 according to equation (3) as performed in sub-process 220. Second PI controller 354 outputs the calculated load sharing value V2 to adder 360.

[0073] Adder 360 of secondary controller 320 can sum the voltage control value V1 with the load sharing value V2 to determine a setpoint V set . It is understood that adder 360 corresponds to equation (8) as performed by sub-process 230.

[0074] Secondary controller 320 can operate continuously on real-time inputs from the bus. These real-time inputs can include or consist of local voltage measurements 328, total load 343, and local current measurements 348. Upon receiving these inputs, setpoint V set is continuously calculated to provide real-time adjustments to voltage control and load sharing of each DC / DC converter 182 of each energy supply 180.

[0075] Accordingly, secondary controller 320 provides a continuous feedback loop for voltage control and load sharing within DC microgrid 130 or hybrid microgrid 100. In particular, based on real-time inputs, a voltage control value V1 is calculated by PI controller 334 to minimize a first error V err1and a voltage control value V2 will be computed by the PI controller 354 to minimize the second error V err2 . Thus, the setpoint V set will be continuously adjusted to minimize these errors V err1 and V err2 .

[0076] The setpoint V set output by the adder 360 can be input to the primary controller 310. In particular, the setpoint V set may be input to the voltage control module 314 of the primary controller 310. It should be understood that the setpoint V set output by a particular secondary controller 320 for a DC / DC converter 182 of one energy supply 180 can be different from the setpoint V set output by another secondary controller 320 for a DC / DC converter 182 of another energy supply 180. In other words, each secondary controller 320 operates independently of the other secondary controllers 320, unless they can rely on one or more common inputs.

[0077] The primary controller 310 can include a droop module 312, a voltage control module 314, and a current control module 316. The droop module 312 can provide droop information to the voltage control module 314, which can utilize the droop information and the setpoint V set received from the secondary controller 320 to provide voltage control information to the current control module 316. The current control module 316 can utilize this voltage control information to provide an output to a pulse width modulation (PWM) generator 370. The PWM generator 370 can control the voltage and current fed to the bus by the energy supply 180 associated with the primary controller 310.

[0078] The secondary controllers 320 are illustrated as being separate and distinct from the primary controller 310. Such embodiments make the setpoint computation modular in that secondary controllers 320 can be swapped in or out as needed (e.g., for replacement, updating, upgrading, etc.). The functional separation in this manner also helps to avoid the occurrence of unmeasurable disturbances in the microgrid. However, in alternative embodiments, the secondary controllers 320 can be integrated into the primary controller 310. For example, one or more, and potentially all, of the functions described above with respect to the secondary controllers 320 can instead be integrated into the primary controller 310 in a non-modular fashion (e.g., into the voltage control module 314). Thus, the use of separate controllers 310 and 320 should not be understood as a limitation on any embodiment unless explicitly stated as a requirement of a particular embodiment.

[0079] Figure 4An example of a processing device 400 that can be used as or in a controller according to an embodiment is illustrated. The processing device 400 can be used as the primary controller 310 and / or the secondary controller 320, or as one or more components of the primary controller 310 and / or the secondary controller 320.

[0080] The processing device 400 includes one or more hardware processors 410. The processor(s) 410 can include a central processing unit (CPU). The processor(s) 410 can also include one or more auxiliary processors, such as a graphics processing unit (GPU), a processor to manage input / output (I / O), a processor to perform floating point mathematical operations, a specialized microprocessor having an architecture suitable for fast execution of signal processing algorithms (e.g., a digital signal processor), a secondary processor subordinate to the primary processing system, additional microprocessors or controllers used in a dual or multiple processor system, and / or a coprocessor. Such auxiliary processors can be discrete processors or can be integrated with the main processor 410. Examples of processors that can be used with the processing device 400 include, but are not limited to, any of the processors available from Intel Corporation of Santa Clara, California (e.g., any of the Pentium®, Core i3®, Core i5®, Core i7®, Xeon®, Itanium®, Celeron®, Atom®, etc.), any of the processors available from Advanced Micro Devices, Inc. (AMD) of Santa Clara, California, any of the processors available from Apple Inc. of Cupertino, California (e.g., A series, M series, etc.), any of the processors available from Samsung Electronics Co., Ltd. of Seoul, Korea (e.g., Exynos®), any of the processors available from NXP Semiconductors of Eindhoven, Netherlands, and / or the like. TM TM TM TM

[0081] Each processor 410 can be connected to a communication bus 405. The communication bus 405 can include a data channel for facilitating the transfer of information between storage devices and other peripheral components of the processing device 400. Further, the communication bus 405 can provide a set of signals for communication with the processor(s) 410, including a data bus, an address bus, and / or a control bus (not shown). The communication bus 405 can include any standard or non-standard bus architecture, such as, for example, a bus architecture compliant with the Industry Standard Architecture (ISA), the Extended Industry Standard Architecture (EISA), the Micro Channel Architecture (MCA), the Peripheral Component Interconnect (PCI) Local Bus, a standard promulgated by the Institute of Electrical and Electronics Engineers (IEEE) including the IEEE 488 General Purpose Interface Bus (GPIB), IEEE 696 / S-100, and / or the like.

[0082] ​​​​The processing device 400 can include a main memory 415 and, optionally, a secondary memory 420. The main memory 415 provides storage of instructions and data for software executing on the processor 410, such as instructions and data implementing one or more of the functions and / or modules discussed herein. It should be understood that programs stored in the memory and executed by the processor 410 can be written and / or compiled according to any suitable language, including but not limited to C / C++, Java, JavaScript, Perl, Visual Basic,.NET, and the like. The main memory 415 is typically a semiconductor-based memory, such as a dynamic random access memory (DRAM) and / or a static random access memory (SRAM). Other semiconductor-based memory types include, for example, synchronous dynamic random access memory (SDRAM), Rambus dynamic random access memory (RDRAM), ferroelectric random access memory (FRAM), and the like, including read only memory (ROM).

[0083] The secondary memory 420 is a non-transitory computer-readable medium on which software can be stored including computer-executable code and / or other data. The software stored on the secondary memory 420 is read into the main memory 415 and executed by the processor(s) 410 on the main memory 415. The secondary memory 420 can include, for example, a semiconductor-based memory such as a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable read-only memory (EEPROM), and flash memory (block-oriented memory similar to EEPROM).

[0084] The processing device 400 can include an I / O interface 435. The I / O interface 435 provides an interface between one or more components of the processing device 400 and one or more input and / or output devices. For example, in the secondary controller 320, the I / O interface 435 can receive the local voltage measurements 328, the total load 343, and / or the local current measurements 348 from one or more sensors in the microgrid, and / or output the setpoint V set to the primary controller 310. As another example, in the primary controller 310, the I / O interface 435 can receive the setpoint V set from the secondary controller 320, and / or output signals to the PWM generator 370.

[0085] The processing device 400 can optionally include a communications interface 440. The communications interface 440 allows software including instructions and / or data to be communicated between the processing device 400 and external systems 445. For example, software including instructions and / or data can be communicated from a network server to the processing device 400 via the communications interface 440 over one or more networks. Any of the inputs and / or outputs described above with respect to the I / O interface 435 can instead be communicated via the communications interface 440. Examples of the communications interface 440 include a built-in network adapter, network interface card (NIC), Personal Computer Memory Card International Association (PCMCIA) network card, card bus network adapter, wireless network adapter, Universal Serial Bus (USB) network adapter, modem, wireless data card, communications port, infrared interface, IEEE 1394 Firewire, and any other device capable of interfacing a processing device 400 with a network or another processing device. The communications interface 440 preferably implements industry- promulgated protocol standards, such as the Ethernet IEEE 802 standards, Fiber Channel, Digital Subscriber Line (DSL), Asymmetric Digital Subscriber Line (ADSL), Frame Relay, Asynchronous Transfer Mode (ATM), Integrated Services Digital Network (ISDN), Personal Communications Service (PCS), Transmission Control Protocol / Internet Protocol (TCP / IP), Serial Line Internet Protocol / Point to Point Protocol (SLIP / PPP), etc., but can also implement customized or non-standard interface protocols.

[0086] Software communicated via the communications interface 440 is typically in the form of electrical communication signals 455. The signals 455 can be provided to the communications interface 440 via a communications channel 450. In embodiments, the communications channel 450 can be a wired or wireless communications link, potentially including a communications network. The communications channel 450 carries the signals 455 and can be implemented using a variety of wired or wireless communication means including wire or cable, fiber optics, conventional phone line, cellular phone link, wireless data communication link, radio-frequency ("RF") link, infrared link, etc.

[0087] Figure 5 A single line diagram illustrating sudden load changes in a hybrid microgrid during islanded conditions is shown according to a simulation example. In the illustrated example, the hybrid microgrid 100 includes an AC bus 510 connected to an AC load 150C. A DC bus 520 is connected to the AC bus 510 via an AC / DC converter 160, and to a DC bus 530 via a DC / DC converter or solid state transformer 170. The AC bus 510 has a reference voltage of 480 volts (V), the DC bus 520 has a reference voltage of 750 V, and the DC bus 530 has a reference voltage of 380 V refThe reference voltage of each bus 510, 520, and 530 should be fixed (i.e., synchronized). In this example, it is assumed that the hybrid microgrid 100 is isolated from the utility grid.

[0088] The DC bus 530 serves the first DC load 150A and the second DC load 150B. The DC bus 530 includes a first battery energy storage system 180A connected to the DC bus 530 via a first DC / DC converter 182A, and a second battery energy storage system 180B connected to the DC bus 530 via a second DC / DC converter 182B. The electrical wire between the first battery energy storage system 180A and the DC bus 530 has a first resistance Rl, and the electrical wire between the second battery energy storage system 180B and the DC bus 530 has a second resistance R2.

[0089] The first DC / DC converter 182A is controlled by a primary controller 310A, for which a setpoint V set is determined by a secondary controller 320A. Similarly, the second DC / DC converter 182B is controlled by a primary controller 310B, for which a setpoint V set is determined by a secondary controller 320B. Each primary controller 310A and 310B and / or each secondary controller 320A and 320B can receive the output of one or more sensors 532 on the DC bus 530. The sensor(s) 532 can include voltage sensors, current sensors, load sensors, and / or the like. For example, the sensors 532 can output local voltage measurements 328, local current measurements 348, and / or total load 343 to the secondary controllers 320A and 320B in real time, which can each utilize these sensor outputs to make independent, real-time adjustments to their respective setpoints V set . Additionally, the secondary controller 310A can utilize the line resistance Rl in a voltage drop estimation unit 324 to calculate a voltage drop V line_drop , and in a power loss estimation unit 344 to calculate a power loss P line_loss . Similarly, the secondary controller 310B can utilize the line resistance R2 in the voltage drop estimation unit 324 to calculate a voltage drop V line_drop , and in the power loss estimation unit 344 to calculate a power loss P line_loss .

[0090] Figure 6A and Figure 6B Figures 1-3 illustrate the use of Figure 5The example hybrid microgrid 100 illustrated in FIG. 1 is subjected to power and voltage profiles achieved by embodiments. In this simulation, the first DC load 150A is connected to the DC bus 530 from the start of the simulation, and the second DC load 150B is suddenly connected to the DC bus 530 via the operating switch fifteen seconds from the start of the simulation. The second DC load 150B is 60 kW. As illustrated, the voltage on the DC bus 530 approaches the reference voltage of 380 V by the twenty-second second marker. Thus, the disclosed embodiments achieve proper voltage control.

[0091] Figure 7 The same simulation depicted in Figure 6A and Figure 6B is used with Figure 5 the example hybrid microgrid 100 illustrated in FIG. 1 is subjected to load sharing achieved by embodiments between the two battery energy storage systems. As illustrated, load sharing is maintained between the first battery energy storage system 180A and the second battery energy storage system 180B. Thus, the disclosed embodiments achieve proper load sharing.

[0092] Furthermore, as a result of independently calculating the load sharing value V2 in each secondary controller 320A and 320B, load sharing is maintained without any communication between the first battery energy storage system 180A and the second battery energy storage system 180B. In other words, each secondary controller 320 can operate independently of, and without communication with, other secondary controllers 320 to achieve voltage control and load sharing.

[0093] Two important control elements in DC microgrids 130 and hybrid microgrids 100 are voltage control of the bus and load sharing between energy supplies 180. As discussed above, the disclosed embodiments are able to achieve both voltage control and load sharing by using a single setpoint V set determined based on (e.g., by summing) the voltage control value V1 and the load sharing value V2, which can be calculated on parallel paths (e.g., within the secondary controller 320) and summed together (e.g., in the sub-process 230, by the adder 360).

[0094] Additionally, the voltage control value V1 can be calculated using the estimated voltage drop V line_drop , and / or the load sharing value V2 can be calculated using the estimated power loss P line_loss . This can improve the transient performance of the combined voltage control and load sharing.

[0095] The disclosed embodiments have been described herein primarily with respect to the DC microgrid 130 or hybrid microgrid 100. However, the disclosed embodiments can be utilized in any system in which a constant energy supply is subject to voltage control and load sharing. Typical use cases for the disclosed embodiments include, but are not limited to, data centers, electric vehicle (EV) charging stations, battery augmentation for storage plants, and the like. The disclosed embodiments can also be used in nested or coordinated DC microgrids 130.

[0096] Example embodiments include, but are not limited to:

[0097] Embodiment 1 : A method of controlling an energy supply, the method comprising: using a controller of the energy supply to: determine a voltage control value based on a first error between a reference parameter of a bus to which the energy supply is electrically connected and a measured parameter of the bus; determine a load sharing value based on a second error between a reference power of the energy supply and a measured power output by the energy supply; determine a setpoint based on the voltage control value and the load sharing value; and output the setpoint to control one or both of a voltage of the bus and a power output by the energy supply in accordance with the setpoint.

[0098] Embodiment 2: The method of embodiment 1, wherein the voltage control value is a first voltage value, the reference parameter is a reference voltage of the bus, and the measured parameter is a measured voltage at the bus.

[0099] Embodiment 3: The method of embodiment 2, further comprising: using the at least one controller to calculate the first error based on a difference between the reference voltage and the measured voltage.

[0100] Embodiment 4: The method of embodiment 3, wherein the first error is calculated further based on an estimated voltage drop on an electrical line between the bus and the energy supply.

[0101] Embodiment 5: The method of embodiment 4, further comprising: using the controller to estimate the voltage drop based on an estimated resistance on the electrical line and a current output by the energy supply.

[0102] Embodiment 6: The method of any one of embodiments 1 to 5, wherein the load sharing value is a second voltage value, and wherein the method further comprises: using the controller to convert the second error from a power value to a voltage value.

[0103] Embodiment 7: The method of embodiment 6, further comprising: using the controller to calculate the second error based on a difference between the reference power and the measured power.

[0104] Example 8: The method of Example 7, wherein the second error is further calculated based on an estimated power loss on an electrical line between the bus and the energy supply.

[0105] Example 9: The method of any one of Examples 6-8, wherein the second error is converted from a power value to a voltage value based on a droop coefficient associated with a direct current (DC) / DC converter of the energy supply.

[0106] Example 10: The method of any one of Examples 1-9, wherein the setpoint is a voltage setpoint.

[0107] Example 11: The method of any one of Examples 1-10, wherein the setpoint is determined as a sum of the voltage control value and the load sharing value.

[0108] Example 12: The method of any one of Examples 1-11, further comprising using the controller to calculate a reference power as a certain proportion of a total load based on a nominal power of the energy supply relative to nominal powers of one or more other energy supplies.

[0109] Example 13: The method of any one of Examples 1-12, wherein the energy supply is a battery energy storage system.

[0110] Example 14: The method of any one of Examples 1-13, wherein the energy supply is a power generator.

[0111] Example 15: The method of any one of Examples 1-14, wherein the controller is a secondary controller, wherein the setpoint is output by the secondary controller to an input of a primary controller of the energy supply, and wherein the method further comprises using the primary controller to control one or both of a voltage of the bus and a power output by the energy supply based on the setpoint output by the secondary controller.

[0112] Example 16: The method of Example 15, wherein the secondary controller outputs the setpoint to a voltage control module of the primary controller.

[0113] Example 17: A controller for an energy supply, the controller configured to: determine a voltage control value based on a first error between a reference parameter of a bus to which the energy supply is electrically connected and a measured parameter of the bus; determine a load sharing value based on a second error between a reference power of the energy supply and a measured power output by the energy supply; determine a setpoint based on the voltage control value and the load sharing value; and output the setpoint to control one or both of a voltage of the bus and a power output by the energy supply in accordance with the setpoint.

[0114] Example 18: The controller of Example 17, wherein the controller is a secondary controller configured to output a setpoint to a voltage control module of a primary controller in a direct current (DC) / DC converter of the energy supply.

[0115] Example 19: The controller of any one of Examples 17 or 18, wherein the energy supply is a battery energy storage system or a power generator within a microgrid.

[0116] Example 20: The controller of any one of Examples 17-19, wherein the voltage control value is a first voltage value, the reference parameter is a reference voltage of the bus, and the measured parameter is a measured voltage at the bus, wherein the first error is calculated as a difference between the reference voltage and the estimated voltage drop on a wire between the bus and the energy supply summed with the measured voltage, wherein the load share value is a second voltage value, wherein the second error is calculated as a difference between the reference power and the estimated power loss on the wire summed with the measured power, and wherein the controller is further configured to convert the second error from a power value to a voltage value.

[0117] The above description of disclosed embodiments is intended to be illustrative and not restrictive. Many embodiments of the application will be readily apparent to those skilled in the art upon reviewing this disclosure. The scope of the inventive subject matter is therefore intended to cover all such modifications and variations of the embodiments described herein that are within the scope of the present application, including full use of the general principles of the present application, as well as the best mode contemplated therefor. Changes can be made in the design of the application without departing from the spirit thereof. Changes might also be necessary in order to adapt commercial applications of this general inventive concept to specific conditions.

[0118] Combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof’ include any combination of one or more items from the listed items A, B, and C, and can include multiples of an item, multiples of a combination, and / or multiples of a combination of items. For example, “at least one of A, B, or C” can include A only, B only, C only, both A and B, both A and C, both B and C, or A and B and C. Similarly, “one or more of A, B, or C” can include A only, B only, C only, both A and B, both A and C, both B and C, or A and B and C. Further, “at least one of A, B, and C” can include A only, B only, C only, both A and B, both A and C, both B and C, or A and B and C. Similarly, “one or more of A, B, and C” can include A only, B only, C only, both A and B, both A and C, both B and C, or A and B and C. Further, “A, B, C, or any combination thereof” can include A only, B only, C only, both A and B, both A and C, both B and C, or A and B and C.

Claims

1. A method for controlling an energy supply component, the method comprising: The following operations are performed using the controller of the energy supply unit: The voltage control value is determined based on a first error between a reference parameter of the bus to which the energy supply device is electrically connected and the measured parameter of the bus. The load sharing value is determined based on a second error between the reference power of the energy supply device and the measured power output by the energy supply device. The setpoint is determined based on the voltage control value and the load sharing value; as well as The setpoint is output to control one or both of the voltage of the bus and the power output by the power supply unit, based on the setpoint.

2. The method according to claim 1, wherein, The voltage control value is a first voltage value, the reference parameter is the reference voltage of the bus, and the measured parameter is the measured voltage at the bus.

3. The method according to claim 2, further comprising: The first error is calculated using the at least one of the controllers based on the difference between the reference voltage and the measured voltage.

4. The method according to claim 3, wherein, The first error is further calculated based on the estimated voltage drop on the wire between the bus and the power supply unit.

5. The method of claim 4, further comprising: The controller is used to estimate the voltage drop based on the estimated resistance on the wire and the current output by the power supply.

6. The method according to any one of claims 1 to 5, wherein, The load sharing value is a second voltage value, and the method further includes: using the controller to convert the second error from a power value to a voltage value.

7. The method of claim 6, further comprising: The controller is used to calculate the second error based on the difference between the reference power and the measured power.

8. The method according to claim 7, wherein, The second error is further calculated based on the estimated power loss on the wires between the bus and the power supply unit.

9. The method according to any one of claims 1 to 5, wherein, The load sharing value is a second voltage value, and the method further includes: using the controller to convert the second error from a power value to a voltage value, using the controller to calculate the second error based on the difference between the reference power and the measured power, and wherein the second error is further calculated based on an estimated power loss on the wire between the bus and the power supply.

10. The method according to claim 6, wherein, The second error is converted from the power value to the voltage value based on the droop factor associated with the DC / DC converter of the power supply device.

11. The method according to any one of claims 1 to 10, wherein, The setpoint is the voltage setpoint.

12. The method according to any one of claims 1 to 11, wherein, The setpoint is determined to be the sum of the voltage control value and the load sharing value.

13. The method according to any one of claims 1 to 12, further comprising: The controller is used to calculate the reference power as a percentage of the total load based on the nominal power of the energy supply relative to the nominal power of one or more other energy supplies.

14. The method according to any one of claims 1 to 13, wherein, The energy supply component is a battery energy storage system.

15. The method according to any one of claims 1 to 14, wherein, The energy supply device is a power generator.

16. The method according to any one of claims 1 to 15, wherein, The controller is a secondary controller, wherein the setpoint is output by the secondary controller to the input of the primary controller of the energy supply, and wherein the method further comprises: using the primary controller to control one or both of the voltage of the bus and the power output by the energy supply based on the setpoint output by the secondary controller.

17. The method according to claim 16, wherein, The secondary controller outputs the setpoint to the voltage control module of the primary controller.

18. A controller for an energy supply device, the controller being configured to: The voltage control value is determined based on a first error between a reference parameter of the bus to which the energy supply device is electrically connected and the measured parameter of the bus. The load sharing value is determined based on a second error between the reference power of the energy supply device and the measured power output by the energy supply device. The setpoint is determined based on the voltage control value and the load sharing value; as well as The setpoint is output to control one or both of the voltage of the bus and the power output by the power supply unit, based on the setpoint.

19. The controller according to claim 18, wherein, The controller is a secondary controller configured to output the setpoint to the voltage control module of the primary controller in the DC / DC converter of the power supply unit.

20. The controller according to claim 19, wherein, The energy supply device is a battery energy storage system or a power generator within the microgrid.

21. The controller according to any one of claims 18 to 20, in, The voltage control value is a first voltage value, the reference parameter is the reference voltage of the bus, and the measured parameter is the measured voltage at the bus. The first error is calculated as the difference between the sum of the following two factors and the measured voltage: the reference voltage and the estimated voltage drop across the wire between the bus and the power supply unit. Wherein, the load sharing value is the second voltage value. The second error is calculated as the difference between the sum of the following two factors and the measured power: the reference power and the estimated power loss on the wire, and The controller is further configured to convert the second error from a power value to a voltage value.

22. The controller according to any one of claims 18 to 20, in, The load sharing value is a second voltage value, and wherein the controller is further configured to: convert the second error from a power value to a voltage value, calculate the second error based on the difference between the reference power and the measured power, and further calculate the second error based on the estimated power loss on the wire between the bus and the power supply.

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