A source-load system anti-flow control method and device and a source-load system

Abstract

The application discloses a source-load system anti-reverse flow control method and device and a source-load system. A power boundary value at a current moment is obtained, a maximum grid-connected point power change rate is obtained according to the power boundary value and a minimum regulation time of the grid-connected point power, a first-order derivative of the grid-connected point power is obtained according to a grid-connected point power sample value at the current moment and a grid-connected point power sample value at a previous moment, a grid-connected point power threshold is determined according to a size relationship between the maximum grid-connected point power change rate and the first-order derivative of the grid-connected point power, and when the current grid-connected point power is less than the grid-connected point power threshold, it is determined that there is a risk of reverse flow at the current moment and an anti-reverse flow operation is performed. The application infers a reverse flow trend based on the first-order derivative of the grid-connected point power, and when it is determined that there is a risk of reverse flow at the current moment, the anti-reverse flow operation is performed in advance at the current moment before the moment when the reverse flow occurs, so that the situation that the grid-connected point has existed for a certain time before the anti-reverse flow operation is performed is effectively avoided, and the safety of the power grid is improved.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, and more specifically, to a method, device, and source-load system for preventing backflow control. Background Technology

[0002] With the continuous development of energy storage technology, source-load systems, which integrate new energy power generation systems, energy storage systems, and electrical load systems, have become a research hotspot. In source-load systems, when the output power of the new energy source exceeds the sum of the energy storage charging power and the electrical load power, or when the sum of the output power of the new energy source and the energy storage discharging power exceeds the electrical load power, the unabsorbed power from the source-load system will be fed into the grid. Since the direction of the current supplied by the source-load system to the grid line is opposite to the direction of the conventional current, this current is called "reverse current" for easy distinction. According to the requirements of the State Grid Corporation of China, the new energy power generation system is designed for irreversible grid connection. When the detected reverse current power exceeds 5% of the rated output power, the source-load system needs to automatically reduce or stop supplying power to the grid line within 0.5s-2s.

[0003] Most existing anti-reverse current control technologies monitor the grid connection point power in real time. When reverse current occurs, they reduce the output power of renewable energy sources or increase the charging power of energy storage (or reduce the discharging power of energy storage). However, due to data transmission delays and control duration, there will be a certain period of reverse current at the grid connection point before the anti-reverse current operation is performed, thus affecting grid security. Summary of the Invention

[0004] In view of this, the present invention discloses a source-load system anti-backflow control method, device and source-load system, which performs anti-backflow operation in advance before the time of backflow occurrence, thereby effectively avoiding the situation that there is already a certain time of backflow at the grid connection point before the anti-backflow operation is performed. It has real-time performance and protection for the power grid, thereby improving the safety of the power grid.

[0005] A method for preventing backflow in a source-load system includes:

[0006] Obtain the power boundary value at the current moment;

[0007] The maximum power change rate at the grid connection point is obtained based on the power boundary value and the minimum adjustment time of the grid connection point power.

[0008] The first derivative of the grid connection point power is obtained based on the current grid connection point power sample value and the previous grid connection point power sample value.

[0009] The grid connection point power threshold is determined based on the relationship between the maximum grid connection point power change rate and the first derivative of the grid connection point power.

[0010] Determine whether the current grid connection point power is less than the grid connection point power threshold;

[0011] If so, it is determined that there is a risk of backflow at the current moment, and anti-backflow operations are performed.

[0012] Optionally, obtaining the power boundary value at the current moment includes:

[0013] Obtain a basic power boundary value, wherein the basic power boundary value is the power output of the power supply that meets a preset condition, and the preset condition is a preset proportion of the average power output of the power supply collected over a preset time period.

[0014] The target cumulative average reverse power is obtained based on the average value of all minimum reverse power within the current operating time of the source-load system and the first preset time interval.

[0015] Based on the current operating time of the source-load system and all minimum power within the second preset time interval, the target cumulative minimum power is obtained, where the second preset time interval is greater than the first preset time interval.

[0016] The power boundary value is obtained based on the basic power boundary value, the target cumulative average reverse power, and the target cumulative minimum power.

[0017] Optionally, the target cumulative average reverse current power is obtained by averaging the minimum reverse current power within the current operating time of the source-load system and the first preset time interval, including:

[0018] Determine whether the current running time of the source-load system has reached an integer multiple of the first preset time interval and whether backflow has occurred;

[0019] If not, the cumulative average reverse current power is obtained by summing all the average reverse current power accumulated during the entire running time from the start time of system operation to the first time, and the cumulative average reverse current power is determined as the target cumulative average reverse current power. Each average reverse current power is the average of all the minimum reverse current power that appears within the corresponding first preset time interval. The first time is the start time of the first preset time interval that is before the current time and closest to the current time.

[0020] If so, obtain all the minimum reverse current power that occurred within the first preset time interval before the current time and closest to the current time, and average all the minimum reverse current power to obtain the target reverse current power mean.

[0021] The target cumulative average reverse current power is obtained based on the target average reverse current power and the cumulative average reverse current power.

[0022] Optionally, the target cumulative minimum power is obtained based on all minimum power within the current operating time of the source-load system and the second preset time interval, including:

[0023] Determine whether the current running time of the source-load system reaches an integer multiple of the second preset time interval and the minimum power is greater than 0, wherein the minimum power is: the minimum power in the second preset time interval before the current time and closest to the current time;

[0024] If not, then determine the sum of all the minimum power accumulated during the entire running time from the start time of system operation to the second time, obtain the cumulative minimum power, and determine the cumulative minimum power as the target cumulative minimum power, wherein the second time is: the start time of the second preset time interval that is before the current time and closest to the current time;

[0025] If so, the target cumulative minimum power is obtained based on the cumulative minimum power and the minimum power.

[0026] Optionally, determining the grid connection point power threshold based on the relationship between the maximum grid connection point power change rate and the first derivative of the grid connection point power includes:

[0027] When the first derivative of the grid connection point power is less than the maximum grid connection point power change rate, the grid connection point power threshold is obtained based on the first derivative of the grid connection point power, the maximum grid connection point power change rate, and the power boundary value.

[0028] When the first derivative of the grid connection point power is not less than the maximum grid connection point power change rate, the power boundary value is determined as the grid connection point power threshold.

[0029] Optionally, performing the anti-backflow operation includes:

[0030] If the source-load system does not include an energy storage module, then:

[0031] The reduction in power output is determined based on the power output, electrical load power, and grid connection point power threshold of the power source-load system.

[0032] If the source-load system includes the energy storage module, then:

[0033] Determine whether the energy storage module is in a charging or discharging state;

[0034] When the energy storage module is in a charging state, it is determined whether the energy storage capacity is not less than the maximum energy storage capacity;

[0035] If so, the energy storage power is determined to be 0, and the power output power reduction is determined based on the power output power in the source-load system, the electrical load power, and the grid connection point power threshold.

[0036] Optionally, when the energy storage capacity is less than the maximum energy storage capacity, the method further includes:

[0037] Determine whether the reduction in the power output of the power source is not greater than the maximum charging power of the energy storage.

[0038] If so, the energy storage power is determined based on the grid connection point power threshold, the power output of the power source, and the power of the electrical load, while keeping the power output of the power source constant.

[0039] If not, the maximum charging power of the energy storage is determined as the energy storage power, and the reduction in the power output is determined based on the power output of the power source, the power load, the maximum charging power of the energy storage, and the power threshold of the grid connection point.

[0040] Optionally, when the energy storage module is in a discharging state, it further includes:

[0041] Determine whether the energy storage capacity is greater than the minimum energy storage capacity;

[0042] If so, the energy storage power is determined based on the grid connection point power threshold, the power output of the power source, and the power of the electrical load, while keeping the power output of the power source constant.

[0043] If not, the energy storage power is determined to be 0, and the power output power reduction is determined based on the power output power, the electrical load power, and the grid connection point power threshold.

[0044] A backflow prevention control device for a source-load system, comprising:

[0045] The acquisition unit is used to acquire the power boundary value at the current moment;

[0046] The power change rate determination unit is used to obtain the maximum power change rate at the grid connection point based on the power boundary value and the minimum adjustment time of the grid connection point power.

[0047] The first derivative of power determination unit is used to obtain the first derivative of the grid-connected power based on the current grid-connected power sampling value and the previous grid-connected power sampling value.

[0048] A power threshold determination unit is used to determine the grid connection point power threshold based on the relationship between the maximum grid connection point power change rate and the first derivative of the grid connection point power.

[0049] The judgment unit is used to determine whether the current grid connection point power is less than the grid connection point power threshold.

[0050] The anti-backflow execution unit is used to determine that there is a risk of backflow at the current moment when the judgment unit determines that it is true, and to perform anti-backflow operation.

[0051] A power source system includes: a power module, an electrical load module, and an energy management server, wherein the energy management server includes the aforementioned power source system anti-backflow control device;

[0052] The power module and the electrical load module are connected via a busbar;

[0053] The energy management server is communicatively connected to the power module.

[0054] Optionally, it also includes: an energy storage module, wherein the power module, the energy storage module, and the electrical load module are connected via a bus; and the energy management server is communicatively connected to the power module and the energy storage module respectively.

[0055] Optional features also include: anti-reverse current relay protection device;

[0056] The anti-reverse current relay protection device is installed at the grid connection point between the grid connection point power meter and the grid side. It is used to disconnect the grid connection point when the anti-reverse current algorithm in the energy management server fails and the detected reverse current exceeds the current threshold.

[0057] As can be seen from the above technical solution, this invention discloses a source-load system anti-backflow control method, device, and source-load system. It obtains the power boundary value at the current moment, calculates the maximum grid-connected point power change rate based on the power boundary value and the minimum adjustment time of the grid-connected point power, and obtains the first derivative of the grid-connected point power based on the sampled power value at the current moment and the sampled power value at the previous moment. It determines the grid-connected point power threshold based on the relationship between the maximum grid-connected point power change rate and the first derivative of the grid-connected point power. When the current grid-connected point power is less than the grid-connected point power threshold, it is determined that there is a risk of backflow at the current moment, and anti-backflow operation is performed. This invention infers the backflow trend based on the first derivative of the grid-connected point power. When it is determined that there is a risk of backflow at the current moment, it performs anti-backflow operation in advance at the current moment, i.e., before the time of backflow occurrence, thereby effectively avoiding the situation where there is already backflow at the grid-connected point for a certain period of time before the anti-backflow operation is performed. It has real-time performance and power grid protection, thus improving the safety of the power grid. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the published drawings without creative effort.

[0059] Figure 1 This is a flowchart of a source-load system anti-backflow control method disclosed in an embodiment of the present invention;

[0060] Figure 2 This is a flowchart of a method for obtaining the power boundary value at the current moment, as disclosed in an embodiment of the present invention.

[0061] Figure 3 This is a flowchart of a method for determining the target cumulative average reverse current power disclosed in an embodiment of the present invention;

[0062] Figure 4 This is a flowchart of a method for determining the target cumulative minimum power disclosed in an embodiment of the present invention;

[0063] Figure 5 This is a graph showing the relationship between the grid point power threshold and the first derivative of the grid connection point power, as disclosed in an embodiment of the present invention.

[0064] Figure 6 This is a flowchart of an anti-reverse current operation method disclosed in an embodiment of the present invention when the energy storage module is in a charging state;

[0065] Figure 7 This is a flowchart of an anti-reverse current operation method disclosed in an embodiment of the present invention when the energy storage module is in a discharging state;

[0066] Figure 8 This is a schematic diagram of the structure of a source-load system anti-backflow control device disclosed in an embodiment of the present invention;

[0067] Figure 9 This is a schematic diagram of a source-load system disclosed in an embodiment of the present invention. Detailed Implementation

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] This invention discloses a method, device, and source-load system for backflow prevention control. The method involves acquiring the current power boundary value, obtaining the maximum grid-connected power change rate based on the power boundary value and the minimum adjustment time of the grid-connected power, obtaining the first derivative of the grid-connected power based on the current and previous sampled power values, and determining the grid-connected power threshold based on the relationship between the maximum grid-connected power change rate and the first derivative. When the current grid-connected power is less than the threshold, a risk of backflow is identified, and backflow prevention is executed. This invention infers backflow trends based on the first derivative of the grid-connected power. When a risk of backflow is identified, backflow prevention is executed before the expected backflow time, effectively preventing backflow from occurring before the backflow prevention operation is performed. This provides real-time performance and grid protection, thereby improving grid security.

[0070] See Figure 1 The present invention discloses a flowchart of a source-load system anti-backflow control method, which is applied to an energy management server in a source-load system. The method includes:

[0071] Step S101: Obtain the power boundary value at the current moment.

[0072] It should be noted that the power boundary value in this embodiment can be determined based on the current operating time, minimum reverse current power, and minimum power of the source-load system. Since the current operating time, minimum reverse current power, and minimum power of the source-load system are constantly changing, the corresponding power boundary value will also change continuously over time.

[0073] In this embodiment, the source in the source-load system refers to a power source, which can be at least one of new energy sources such as photovoltaics and wind power.

[0074] Step S102: Based on the power boundary value and the minimum adjustment time of the grid connection point power, obtain the maximum grid connection point power change rate.

[0075] The expression for the maximum power change rate at the grid connection point is as follows:

[0076]

[0077] In the formula, This represents the maximum rate of change of power at the grid connection point. Represents the power boundary value, t design This represents the minimum adjustment time of the grid-connected power. In practical applications, when the source-load system does not contain an energy storage module, t design The transmission delay from the energy management server to the power module can be used as a reference. When the source-load system includes an energy storage module, tdesign The transmission latency from the energy management server to the power module and energy storage module can be used.

[0078] Step S103: Obtain the first derivative of the grid connection point power based on the current grid connection point power sample value and the previous grid connection point power sample value.

[0079] The expression for the first derivative of the power at the grid connection point is as follows:

[0080]

[0081] In the formula, P represents the first derivative of the power at the grid connection point. g (t) represents the current grid-connected power sampling value, P g (t-Δt) represents the sampled power value at the grid connection point at the previous moment, and Δt represents the sampling time.

[0082] Step S104: Determine the grid connection point power threshold based on the relationship between the maximum grid connection point power change rate and the first derivative of the grid connection point power.

[0083] Step S105: Determine whether the current grid connection point power is less than the grid connection point power threshold. If so, proceed to step S106.

[0084] Step S106: Determine if there is a risk of backflow at the current moment and perform anti-backflow operation.

[0085] In summary, this invention discloses a backflow prevention control method for a source-load system. It obtains the current power boundary value, calculates the maximum power change rate at the grid connection point based on the power boundary value and the minimum adjustment time of the grid connection point power, and obtains the first derivative of the grid connection point power based on the current and previous sampled power values. A grid connection point power threshold is determined based on the relationship between the maximum power change rate and the first derivative of the grid connection point power. When the current grid connection point power is less than the threshold, a backflow risk is identified, and backflow prevention is executed. This invention infers the backflow trend based on the first derivative of the grid connection point power. When a backflow risk is identified, backflow prevention is executed before the backflow occurs, effectively preventing backflow from occurring at the grid connection point before the backflow prevention operation is executed. This method offers real-time performance and grid protection, thereby improving grid security.

[0086] In addition, compared with the anti-backflow control with predictive function in traditional solutions, the present invention does not require meteorological data and high-configuration industrial control computers. It can achieve the effect of active anti-backflow with a small amount of calculation.

[0087] To further optimize the above embodiments, see [link to relevant documentation]. Figure 2 The present invention discloses a flowchart of a method for obtaining the power boundary value at the current moment, the method comprising:

[0088] Step S201: Obtain the basic power boundary value.

[0089] In practical applications, the power output can be collected in real time, and the power output that meets the preset conditions can be used as the basic power boundary value. The preset condition is a preset percentage of the average power output of the power source collected in a preset time period (e.g., the first 5 minutes), such as 5%.

[0090] Step S202: Based on the current running time of the source-load system and the average value of all minimum reverse current power within the first preset time interval, obtain the target cumulative average reverse current power.

[0091] The value of the first preset time period is determined according to actual needs, such as 1 hour, but this invention does not limit it.

[0092] Step S203: Based on the current running time of the source-load system and all minimum power within the second preset time interval, obtain the target cumulative minimum power.

[0093] The value of the second preset time period is determined according to actual needs, such as 1 day, but this invention does not limit it.

[0094] It should be noted that the second preset time interval is greater than the first preset time interval. In practical applications, the second preset time interval can be an integer multiple of the first preset time interval.

[0095] Step S204: Obtain the power boundary value based on the basic power boundary value, the target cumulative average reverse power, and the target cumulative minimum power.

[0096] Specifically, the expression for the power boundary value is as follows:

[0097]

[0098] In the formula, Indicates the power boundary value. Indicates the baseline power boundary value. This represents the target cumulative average reverse current power. This represents the target cumulative minimum power.

[0099] To further optimize the above embodiments, see [link to relevant documentation]. Figure 3 The present invention discloses a flowchart of a method for determining a target cumulative average reverse current power, the method comprising:

[0100] Step S301: Determine whether the current running time of the source-load system has reached an integer multiple of the first preset time interval and whether backflow has occurred. If not, proceed to step S302; if yes, proceed to step S303.

[0101] Step S302: Determine the sum of the average values ​​of all reverse current power accumulated during the entire operating time from the start time of system operation to the first moment to obtain the cumulative average reverse current power, and determine the cumulative average reverse current power as the target cumulative average reverse current power.

[0102] The mean power of each countercurrent is the average of all minimum countercurrent powers that occur within the corresponding first preset time interval.

[0103] The first moment is the start time of the first preset time interval that is closest to the current moment and precedes the current moment.

[0104] Specifically, when the current operating time of the source-load system is not an integer multiple of the first preset time interval and / or no reverse flow occurs, the target cumulative average reverse flow power is calculated according to the following formula:

[0105]

[0106] In the formula, The target cumulative average reverse current power is represented, t represents the current time in seconds, t1 represents the first preset time interval, and (t-t1) represents the total running time from the start of system operation to the first time interval. This represents the sum of the average values ​​of all reverse current power accumulated during the entire operating time from the start of system operation to the first moment, also known as the cumulative average reverse current power.

[0107] Step S303: Obtain all minimum reverse current power occurring within the first preset time interval before and closest to the current time, and average all the minimum reverse current power to obtain the target reverse current power mean.

[0108] Step S304: Obtain the target cumulative average reverse current power based on the target average reverse current power and the cumulative average reverse current power.

[0109] Specifically, when the current operating time of the source-load system reaches an integer multiple of the first preset time interval and reverse flow occurs, the target cumulative average reverse flow power is calculated according to the following formula:

[0110]

[0111] In the formula, This represents the average value of the target countercurrent power.

[0112] To further optimize the above embodiments, see [link to relevant documentation]. Figure 4The present invention discloses a flowchart of a method for determining a target cumulative minimum power, the method comprising:

[0113] Step S401: Determine whether the current running time of the source-load system has reached an integer multiple of the second preset time interval and the minimum power is greater than 0. If not, proceed to step S402; if yes, proceed to step S403.

[0114] The minimum power is defined as the minimum power within the second preset time interval that is closest to the current time, prior to the current time.

[0115] Step S402: Determine the sum of all the minimum power accumulated during the entire running time from the start time of system operation to the second time, obtain the cumulative minimum power, and determine the cumulative minimum power as the target cumulative minimum power.

[0116] The second moment is the start time of the second preset time interval that is closest to the current moment and precedes the current moment.

[0117] Specifically, if the current operating time of the source-load system does not reach an integer multiple of the second preset time interval and / or the minimum power... At that time, the target cumulative minimum power is calculated according to the following formula:

[0118]

[0119] In the formula, The target cumulative minimum power is represented by t, where t represents the current time in seconds, t2 represents the second preset time interval, and (t-t2) represents the total running time from the start of system operation to the second time interval. This represents the sum of all minimum power accumulated during the entire operating time from the start of system operation to the second moment, also known as the cumulative minimum power.

[0120] Step S403: Obtain the target cumulative minimum power based on the cumulative minimum power and the minimum power.

[0121] Specifically, when the current operating time of the source-load system reaches an integer multiple of the second preset time interval and the power is at its minimum. The target cumulative minimum power is calculated using the following formula:

[0122]

[0123] In the formula, This indicates the minimum power.

[0124] To further optimize the above embodiments, step S104 may specifically include:

[0125] (1) When the first derivative of the grid connection point power is less than the maximum grid connection point power change rate, the grid connection point power threshold is obtained based on the first derivative of the grid connection point power, the maximum grid connection point power change rate, and the power boundary value.

[0126] For details, see Figure 5 The graph showing the relationship between the grid connection point power threshold and the first derivative of the grid connection point power is as follows: Figure 5 It can be seen from this:

[0127] when At that time, the power threshold of the grid connection point The expression is as follows:

[0128]

[0129] In the formula, Here, k is the first derivative of the power at the grid connection point, and k is the slope, representing the power supply variation coefficient, derived from the maximum power variation rate at the grid connection point. Sure, For power boundary values, t design This indicates the minimum adjustment time for the grid connection point's power.

[0130] (2) When the first derivative of the power at the grid connection point is not less than the maximum power change rate at the grid connection point, the power boundary value is determined as the power threshold at the grid connection point.

[0131] Specifically, when At that time, the power threshold of the grid connection point The expression is as follows:

[0132]

[0133] In summary, this invention obtains an approximately optimal grid connection point power threshold by comparing the first derivative of the grid connection point power with the maximum rate of change of grid connection point power. This allows for timely identification of the risk of reverse current occurrence, making the energy scheduling of the source-load system more rational and improving the power utilization rate of the source-load system.

[0134] When it is determined that there is a risk of backflow at the current moment, in order to avoid backflow at the grid connection point for a certain period of time before the anti-backflow operation is performed, which would affect the safety of the power grid, the present invention performs anti-backflow operation in advance before the backflow occurs.

[0135] If the source-load system does not include an energy storage module, then:

[0136] The reduction in power output is determined based on the power output, electrical load power, and grid connection point power threshold in the power source-load system.

[0137] If the source-load system includes an energy storage module, then refer to [reference needed]. Figure 6The present invention discloses a flowchart of an anti-reverse current operation method when an energy storage module is in a charging state. The method includes:

[0138] Step S501: Determine whether the energy storage module is in a charging or discharging state.

[0139] In practical applications, the energy storage module can be determined to be in a charging or discharging state based on the energy storage flag.

[0140] When the energy storage flag bit ESS When = 1, it indicates that the energy storage module is in a charging state;

[0141] When the energy storage flag bit ESS When the value is 0, it indicates that the energy storage module is in a discharging state. At this time, the power output of the source-load system is weak or non-existent, for example, the photovoltaic power is very weak or non-existent.

[0142] Step S502: When the energy storage module is in the charging state, determine whether the energy storage capacity is not less than the maximum energy storage capacity. If yes, proceed to step S503; otherwise, proceed to step S504.

[0143] Step S503: Determine that the energy storage power is 0, and determine the amount of power output reduction based on the power output, electrical load power and grid connection point power threshold in the source-load system.

[0144] In this embodiment, the energy storage capacity is represented as SOC, and the maximum energy storage capacity is also represented as SOC. max .

[0145] When SOC≥SOC max At that time, the energy storage power is determined to be 0 and the power output power reduction ΔP is determined to be 0. source The decrease in power output ΔP source The expression is as follows:

[0146]

[0147] In the formula, P source P represents the power output of the power supply. load Indicates electrical load power. This indicates the power threshold at the grid connection point.

[0148] Step S504: Determine whether the reduction in power output is not greater than the maximum charging power of energy storage. If yes, proceed to step S505; otherwise, proceed to step S506.

[0149] Step S505: Determine the energy storage power based on the grid connection point power threshold, power output, and electrical load power, while keeping the power output constant;

[0150] In this embodiment, when SOC < SOC max and At that time, P B_max This indicates the maximum charging power of the energy storage; the default maximum discharging power is -P. B_max Then the energy storage capacity is And keep the power output constant.

[0151] Step S506: Determine the maximum charging power of energy storage as the energy storage power, and determine the reduction in power output power based on the power output power, electrical load power, maximum charging power of energy storage, and grid connection point power threshold.

[0152] In this embodiment, when SOC < SOC max and When the energy storage capacity is P, then the energy storage capacity is P. B_max The amount of power output reduction

[0153] It should be noted that the anti-reverse current operation performed when the energy storage module is in the charging state is different from the anti-reverse current operation performed when the energy storage module is in the discharging state.

[0154] Therefore, when the energy storage module is in a discharging state, the anti-reverse current operation performed is as follows: Figure 7 As shown.

[0155] See Figure 7 The present invention discloses a flowchart of an anti-reverse current operation method when the energy storage module is in a discharging state. The method includes:

[0156] Step S601: Determine whether the energy storage capacity is greater than the minimum energy storage capacity. If yes, proceed to step S602; otherwise, proceed to step S603.

[0157] Step S602: Determine the energy storage power based on the grid connection point power threshold, power output, and power of the electrical load module, while keeping the power output constant;

[0158] In this embodiment, the energy storage capacity is represented by SOC, and the minimum energy storage capacity is also represented by SOC. min .

[0159] When the energy storage flag bit ESS When SOC = 0, if SOC > S m O i C, then the energy storage capacity is And keep the power output constant.

[0160] Step S603: Determine that the energy storage power is 0, and determine the power reduction amount based on the power output, electrical load power and grid connection point power threshold.

[0161] When the energy storage flag bit ESS When = 0, if SOC ≤ SOC min Then the energy storage power is 0, and the power output of the power source decreases by [amount missing].

[0162] In this invention, if the current grid connection point power P g ≥ Grid connection point power threshold If there is no risk of backflow at the current moment, then neither the photovoltaic power generation module nor the energy storage module will operate. In this case, let t = t + Δt, where t represents the current moment in seconds, and Δt represents the sampling time of the energy management server, for example, 0.05s. When (t + Δt) < t max , t max If the total system runtime is t, return to step S301; otherwise, if (t+Δt)≥t max Then the control system will end operation.

[0163] By taking into account data such as the sampling time of the energy management server, this invention is more in line with actual industrial scenarios and facilitates the implementation of anti-backflow function under different controller models and different installation scenarios.

[0164] Corresponding to the above method embodiments, the present invention also discloses a source-load system anti-backflow control device.

[0165] See Figure 8 The present invention discloses a schematic diagram of a backflow prevention control device for a source-load system. This device is applied to an energy management server in a source-load system and includes:

[0166] Acquisition unit 701 is used to acquire the power boundary value at the current moment;

[0167] It should be noted that the power boundary value in this embodiment can be determined based on the current operating time, minimum reverse current power, and minimum power of the source-load system. Since the current operating time, minimum reverse current power, and minimum power of the source-load system are constantly changing, the corresponding power boundary value will also change continuously over time.

[0168] The power change rate determination unit 702 is used to obtain the maximum power change rate at the grid connection point based on the power boundary value and the minimum adjustment time of the grid connection point power.

[0169] The expression for the maximum power change rate at the grid connection point is as follows:

[0170]

[0171] In the formula, This represents the maximum rate of change of power at the grid connection point. Represents the power boundary value, t design This represents the minimum adjustment time of the grid-connected power. In practical applications, when the source-load system does not contain an energy storage module, t design The transmission delay from the energy management server to the power module can be used as a reference. When the source-load system includes an energy storage module, t design The transmission latency from the energy management server to the power module and energy storage module can be used.

[0172] The power first derivative determination unit 703 is used to obtain the grid connection point power first derivative based on the grid connection point power sample value at the current time and the grid connection point power sample value at the previous time.

[0173] The expression for the first derivative of the power at the grid connection point is as follows:

[0174]

[0175] In the formula, P represents the first derivative of the power at the grid connection point. g (t) represents the current grid-connected power sampling value, P g (t-Δt) represents the sampled power value at the grid connection point at the previous moment, and Δt represents the sampling time.

[0176] The power threshold determination unit 704 is used to determine the grid connection point power threshold based on the relationship between the maximum grid connection point power change rate and the first derivative of the grid connection point power.

[0177] The judgment unit 705 is used to determine whether the current grid connection point power is less than the grid connection point power threshold;

[0178] The anti-backflow execution unit 706 is used to determine that there is a risk of backflow at the current moment when the judgment unit 705 determines that it is true, and to perform anti-backflow operation.

[0179] In summary, this invention discloses a backflow prevention control device for a source-load system. It acquires the current power boundary value, obtains the maximum grid-connected power change rate based on the power boundary value and the minimum adjustment time of the grid-connected power, and obtains the first derivative of the grid-connected power based on the current and previous sampled power values. It determines the grid-connected power threshold based on the relationship between the maximum grid-connected power change rate and the first derivative of the grid-connected power. When the current grid-connected power is less than the threshold, it is determined that there is a risk of backflow, and an anti-backflow operation is performed. This invention infers the backflow trend based on the first derivative of the grid-connected power. When a risk of backflow is determined, it performs the anti-backflow operation in advance, before the actual backflow occurs, effectively preventing backflow from occurring at the grid-connected point before the anti-backflow operation is executed. This provides real-time performance and grid protection, thereby improving grid security.

[0180] It should be noted that for the specific working principles of each component in the device embodiment, please refer to the corresponding section of the method embodiment, which will not be repeated here.

[0181] Corresponding to the above embodiments, the present invention also discloses a source-load system, including: a power module, an electrical load module, and an energy management server, wherein the energy management server includes a source-load system anti-reverse flow control device;

[0182] The power module and the electrical load module are connected via a busbar;

[0183] The energy management server is communicatively connected to the power module.

[0184] To further optimize the above embodiments, the power supply system may further include: an energy storage module, wherein the power supply module, the energy storage module, and the electrical load module are connected via a bus; and the energy management server is communicatively connected to the power supply module and the energy storage module respectively.

[0185] In practical applications, source-load systems can be photovoltaic-storage-load systems, wind-storage-load systems, wind-solar-storage-load systems, photovoltaic-load systems, etc. The following explanation uses a photovoltaic-storage-load system as an example:

[0186] See Figure 9 The present invention discloses a schematic diagram of a photovoltaic power generation system, which includes a photovoltaic power generation module 10, an energy storage module 20, an electrical load module 30, and an energy management server 40.

[0187] Among them, the energy management server 40 includes Figure 8 The embodiment shown illustrates a backflow prevention control device for a photovoltaic energy storage system.

[0188] The photovoltaic power generation module 10, the energy storage module 20, and the electrical load module 30 are connected via a busbar.

[0189] Specifically, the photovoltaic power generation module 10 includes a photovoltaic module 11 and a photovoltaic inverter 12. The photovoltaic module 11 is connected to the busbar through the photovoltaic inverter 12. In this embodiment, the busbar is mainly an AC busbar.

[0190] The energy storage module 20 includes an energy storage converter 21 and an energy storage device 22, which is connected to the bus via the energy storage converter 21.

[0191] The energy management server 40 is communicatively connected to the photovoltaic power generation module 10 and the energy storage module 20, respectively.

[0192] Specifically, the energy management server 40 is connected to the photovoltaic inverter 12 in the photovoltaic power generation module 10 and the energy storage converter 21 in the energy storage module 20.

[0193] It should be noted that the grid connection point of the photovoltaic-storage-load system is designed on the low-voltage side of transformer 50. The photovoltaic power generation module 10, energy storage module 20, load module 30, and the grid connection point all have equipment for real-time monitoring of power data (i.e.,...). Figure 9 (The various power meters 50 shown in the figure). In this embodiment, the electrical load module 30 is uncontrollable; therefore, the energy management server 40 of the present invention only controls the photovoltaic inverter 12 and the energy storage converter 21. In practical applications, the power flow into the bus can be defined as negative, and the power flow out of the bus as positive. For example, the power flow value is negative when the photovoltaic power generation module 10 generates electricity.

[0194] It should be noted that the process of the energy management server 40 performing the anti-backflow control of the photovoltaic storage system can be found in the corresponding part of the above embodiments, and will not be repeated here.

[0195] In summary, this invention discloses a photovoltaic-storage-load system, including a photovoltaic power generation module 10, an energy storage module 20, an electrical load module 30, and an energy management server 40. The energy management server 40 acquires the power boundary value at the current moment, obtains the maximum grid-connected power change rate based on the power boundary value and the minimum adjustment time of the grid-connected power, obtains the first derivative of the grid-connected power based on the sampled power value at the current moment and the sampled power value at the previous moment, and determines the grid-connected power threshold based on the relationship between the maximum grid-connected power change rate and the first derivative of the grid-connected power. When the current grid-connected power is less than the grid-connected power threshold, it is determined that there is a risk of reverse current occurrence at the current moment, and anti-reverse current operation is performed. This invention infers the reverse current trend based on the first derivative of the grid-connected power. When it is determined that there is a risk of reverse current occurrence at the current moment, it performs anti-reverse current operation in advance at the current moment, that is, before the moment of reverse current occurrence, thereby effectively avoiding the situation where there is already a certain amount of reverse current at the grid-connected point before the anti-reverse current operation is performed. It has real-time performance and grid protection, thereby improving the safety of the power grid.

[0196] To further optimize the above embodiments, the source-load system may also include: a reverse current protection relay device 60;

[0197] The anti-reverse current relay protection device 60 is installed at the grid connection point between the grid connection point power meter and the grid side. It is used to disconnect the grid connection point when the anti-reverse current algorithm in the energy management server 40 fails and the detected reverse current exceeds the current threshold.

[0198] It should be noted that the grid connection point power meter described in this embodiment is also the power meter installed between the source-load system and the power grid.

[0199] This invention takes into account situations such as control algorithm failure or controller damage, by adding a reverse current protection relay at the grid connection point, thereby further improving the reliability of the source-load system's grid-connected operation.

[0200] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0201] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0202] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preventing backflow control in a source-load system, characterized in that, include: Obtain the power boundary value at the current moment; The maximum power change rate at the grid connection point is obtained based on the power boundary value and the minimum adjustment time of the grid connection point power. The first derivative of the grid connection point power is obtained based on the current grid connection point power sample value and the previous grid connection point power sample value. When the first derivative of the grid connection point power is less than the maximum grid connection point power change rate, the grid connection point power threshold is obtained based on the first derivative of the grid connection point power, the maximum grid connection point power change rate, and the power boundary value; when the first derivative of the grid connection point power is not less than the maximum grid connection point power change rate, the power boundary value is determined as the grid connection point power threshold. Determine whether the current grid connection point power is less than the grid connection point power threshold; If so, it is determined that there is a risk of backflow at the current moment, and anti-backflow operations are performed.

2. The source-load system anti-backflow control method according to claim 1, characterized in that, The step of obtaining the power boundary value at the current moment includes: Obtain a basic power boundary value, wherein the basic power boundary value is the power output of the power supply that meets a preset condition, and the preset condition is a preset proportion of the average power output of the power supply collected over a preset time period. The target cumulative average reverse power is obtained based on the average value of all minimum reverse power within the current operating time of the source-load system and the first preset time interval. Based on the current operating time of the source-load system and all minimum power within the second preset time interval, the target cumulative minimum power is obtained, where the second preset time interval is greater than the first preset time interval. The power boundary value is obtained based on the basic power boundary value, the target cumulative average reverse power, and the target cumulative minimum power.

3. The source-load system anti-backflow control method according to claim 2, characterized in that, The target cumulative average reverse current power is obtained by averaging all minimum reverse current power within the current operating time of the source-load system and the first preset time interval, including: Determine whether the current running time of the source-load system has reached an integer multiple of the first preset time interval and whether backflow has occurred; If not, the cumulative average reverse current power is obtained by summing all the average reverse current power accumulated during the entire running time from the start time of system operation to the first time, and the cumulative average reverse current power is determined as the target cumulative average reverse current power. Each average reverse current power is the average of all the minimum reverse current power that appears within the corresponding first preset time interval. The first time is the start time of the first preset time interval that is before the current time and closest to the current time. If so, obtain all the minimum reverse current power that occurred within the first preset time interval before the current time and closest to the current time, and average all the minimum reverse current power to obtain the target reverse current power mean. The target cumulative average reverse current power is obtained based on the target average reverse current power and the cumulative average reverse current power.

4. The source-load system anti-backflow control method according to claim 2, characterized in that, Based on the current operating time of the source-load system and all minimum power within the second preset time interval, the target cumulative minimum power is obtained, including: Determine whether the current running time of the source-load system reaches an integer multiple of the second preset time interval and the minimum power is greater than 0, wherein the minimum power is: the minimum power in the second preset time interval before the current time and closest to the current time; If not, then determine the sum of all the minimum power accumulated during the entire running time from the start time of system operation to the second time, obtain the cumulative minimum power, and determine the cumulative minimum power as the target cumulative minimum power, wherein the second time is: the start time of the second preset time interval that is before the current time and closest to the current time; If so, the target cumulative minimum power is obtained based on the cumulative minimum power and the minimum power.

5. The source-load system anti-backflow control method according to claim 1, characterized in that, The execution of the anti-backflow operation includes: If the source-load system does not include an energy storage module, then: The reduction in power output is determined based on the power output, electrical load power, and grid connection point power threshold of the power source-load system. If the source-load system includes the energy storage module, then: Determine whether the energy storage module is in a charging or discharging state; When the energy storage module is in a charging state, it is determined whether the energy storage capacity is not less than the maximum energy storage capacity; If so, the energy storage power is determined to be 0, and the power output power reduction is determined based on the power output power in the source-load system, the electrical load power, and the grid connection point power threshold.

6. The source-load system anti-backflow control method according to claim 5, characterized in that, When the energy storage capacity is less than the maximum energy storage capacity, the method further includes: Determine whether the reduction in the power output of the power source is not greater than the maximum charging power of the energy storage. If so, the energy storage power is determined based on the grid connection point power threshold, the power output of the power source, and the power of the electrical load, while keeping the power output of the power source constant. If not, the maximum charging power of the energy storage is determined as the energy storage power, and the reduction in the power output is determined based on the power output of the power source, the power load, the maximum charging power of the energy storage, and the power threshold of the grid connection point.

7. The source-load system anti-backflow control method according to claim 5, characterized in that, When the energy storage module is in a discharging state, it also includes: Determine whether the energy storage capacity is greater than the minimum energy storage capacity; If so, the energy storage power is determined based on the grid connection point power threshold, the power output of the power source, and the power of the electrical load, while keeping the power output of the power source constant. If not, the energy storage power is determined to be 0, and the power output power reduction is determined based on the power output power, the electrical load power, and the grid connection point power threshold.

8. A backflow prevention control device for a source-load system, characterized in that, include: The acquisition unit is used to acquire the power boundary value at the current moment; The power change rate determination unit is used to obtain the maximum power change rate at the grid connection point based on the power boundary value and the minimum adjustment time of the grid connection point power. The first derivative of power determination unit is used to obtain the first derivative of the grid-connected power based on the current grid-connected power sampling value and the previous grid-connected power sampling value. The power threshold determination unit is used to obtain the grid connection point power threshold based on the first derivative of the grid connection point power, the maximum grid connection point power change rate, and the power boundary value when the first derivative of the grid connection point power is less than the maximum grid connection point power change rate; and to determine the power boundary value as the grid connection point power threshold when the first derivative of the grid connection point power is not less than the maximum grid connection point power change rate. The judgment unit is used to determine whether the current grid connection point power is less than the grid connection point power threshold. The anti-backflow execution unit is used to determine that there is a risk of backflow at the current moment when the judgment unit determines that it is true, and to perform anti-backflow operation.

9. A source-load system, characterized in that, include: The power supply module, the electrical load module, and the energy management server, wherein the energy management server includes the anti-backflow control device for the source-load system as described in claim 8; The power module and the electrical load module are connected via a busbar; The energy management server is communicatively connected to the power module.

10. The source-load system according to claim 9, characterized in that, Also includes: The energy storage module, the power module, and the electrical load module are connected via a busbar; the energy management server is communicatively connected to the power module and the energy storage module respectively.

11. The source-load system according to claim 9, characterized in that, Also includes: Anti-reverse current relay protection device; The anti-reverse current relay protection device is installed at the grid connection point between the grid connection point power meter and the grid side. It is used to disconnect the grid connection point when the anti-reverse current algorithm in the energy management server fails and the detected reverse current exceeds the current threshold.

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