A load monitoring and early warning method and system for an uninterruptible power supply system

Abstract

The present invention provides a load monitoring and early warning method and system for an uninterruptible power supply system, comprising collecting the current signal of each load of the uninterruptible power supply system at the load end; monitoring all current signals, and obtaining the current peak value of each load in the current monitoring cycle based on all current signals; monitoring the system overload condition of the uninterruptible power supply system based on the current peak value of each load; setting the monitoring signal used to monitor the system overload condition in parallel with the monitoring signal originally used to monitor the load overload condition of a single device in the UPS device; and performing load monitoring and early warning on the uninterruptible power supply system based on the two monitoring signals. By obtaining the current peak value of each load and participating in the overload monitoring calculation of the system, the present invention can solve the problem that when all load cables are connected in series with a group of mutual inductors for measurement, the true overall load peak value of the system cannot be obtained due to phase influence. At the same time, the overload condition of the system can be effectively monitored.

Description

Technical Field

[0001] The present invention belongs to the technical field of maintenance and application of uninterruptible power supply systems in places such as substations, and particularly relates to a load monitoring and early warning method and system for an uninterruptible power supply system. Background Art

[0002] An uninterruptible power supply (UPS) system is an AC power source with energy storage devices, primarily used to provide uninterruptible power to critical substation equipment requiring high reliability. It consists of two redundant UPS units operating in a single-bus, segmented mains connection mode. Key loads include automation system computers and switches, remote control equipment (RTUs), fire alarm systems, dispatching data network switches, secondary safety protection equipment, five-security workstations, and access control systems.

[0003] When the UPS device is overloaded due to excessive load, the load will be switched to the AC power supply through the bypass switch. At this time, the above-mentioned equipment will be at risk of power outage when the entire station AC voltage drops. The power outage of these equipment will directly lead to the loss of remote monitoring and paralysis of the substation.

[0004] According to relevant technical specifications, the output rated power of either UPS unit should be no less than 1.2 times the total actual capacity of all loads, ensuring that the UPS system still has 20% redundant capacity when one UPS unit is out of service. Existing UPS units can only issue overload alarms for their own loads. When the uninterruptible power supply system consists of two redundant UPS units, the monitoring unit itself cannot effectively monitor and calculate the load current of the two UPS units. Although the load of the uninterruptible power supply system within the substation met the above requirements according to the construction design during the initial operation of the substation, as the load within the substation gradually increased, the load of a single UPS unit did not exceed the specified value, but the total system load exceeded the specified value. When one UPS unit fails and is out of service, and the other UPS unit carries the full load, there is a high probability of overload, resulting in a significant operational risk. Therefore, it is necessary to carry out technical modifications to address these risks. Summary of the Invention

[0005] In view of this, the present invention aims to provide an operation monitoring method and system for an uninterruptible power supply system, which performs load monitoring on two redundant UPS devices to prevent the other device from being overloaded after one device fails and is decommissioned.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a load monitoring and early warning method for an uninterruptible power supply system, comprising the following steps:

[0008] Collect the current signal of each load of the uninterruptible power supply system at the load end;

[0009] Monitor all current signals and calculate the peak current of each load within the current monitoring period based on all current signals;

[0010] Monitor the system overload of the UPS system based on the current peak value of each load;

[0011] The monitoring signal for monitoring system overload is connected in parallel with the monitoring signal originally used to monitor the load overload of a single device in the UPS device;

[0012] The uninterruptible power supply system is monitored and warned of load based on two monitoring signals.

[0013] Furthermore, the current signals of each load of the uninterruptible power supply system are collected at the load end, specifically:

[0014] A digital AC transformer is used at the load end to collect the current signal of each load of the uninterruptible power supply system according to the set sampling frequency to obtain the current sampling signal of each load.

[0015] Furthermore, the current peak is calculated according to the following formula:

[0016] Y=I_ mean +(k*I_ std )

[0017] Where Y is the peak current, I_ mean is the mean value of the current sampling signal, I_ std is the standard deviation of the current sampling signal, k is the coefficient, and k∈[2,4].

[0018] Furthermore, the system overload condition of the uninterruptible power supply system is monitored based on the current peak value of each load, specifically:

[0019] Set the system overload threshold;

[0020] Calculate the total peak current of all loads and compare it with the system overload threshold;

[0021] If it is greater than the system overload threshold, it is considered that the uninterruptible power supply system has a systematic overload or a transient overload caused by a dynamic load.

[0022] Furthermore, the system overload threshold is calculated according to the following formula:

[0023]

[0024] Where Y setis the system overload threshold, Y0 is the upper limit of the load current of the entire station, δ is the correction coefficient, cos(η) is the actual power factor, and cos(φ) is the rated power factor.

[0025] In a second aspect, the present invention provides a load monitoring and early warning system for an uninterruptible power supply system, comprising:

[0026] A current acquisition unit is used to collect the current signal of each load of the uninterruptible power supply system at the load end;

[0027] A signal processing unit is used to monitor all current signals and calculate the current peak value of each load in the current monitoring period based on all current signals;

[0028] A system overload monitoring unit, configured to monitor the system overload condition of the uninterruptible power supply system based on the peak current of each load; wherein the monitoring signal for monitoring the system overload condition is connected in parallel with the monitoring signal originally used to monitor the load overload condition of a single device in the UPS device;

[0029] The early warning unit is used to perform load monitoring and early warning on the uninterruptible power supply system based on two monitoring signals.

[0030] Furthermore, in the current acquisition unit, the current signal of each load of the uninterruptible power supply system is collected at the load end, specifically:

[0031] A digital AC transformer is used at the load end to collect the current signal of each load of the uninterruptible power supply system according to the set sampling frequency to obtain the current sampling signal of each load.

[0032] Furthermore, in the signal processing unit, the current peak is calculated according to the following formula:

[0033] Y=I_ mean +(k*I_ std )

[0034] Where Y is the peak current, I_ mean is the mean value of the current sampling signal, I_ std is the standard deviation of the current sampling signal, k is the coefficient, and k∈[2,4].

[0035] Furthermore, in the system overload monitoring unit, the system overload condition of the uninterruptible power supply system is monitored based on the current peak value of each load, specifically:

[0036] Set the system overload threshold;

[0037] Calculate the total peak current of all loads and compare it with the system overload threshold;

[0038] If it is greater than the system overload threshold, it is considered that the uninterruptible power supply system has a systematic overload or a transient overload caused by a dynamic load.

[0039] Furthermore, in the system overload monitoring unit, the system overload threshold is calculated according to the following formula:

[0040]

[0041] Where Y set is the system overload threshold, Y0 is the upper limit of the load current of the entire station, δ is the correction coefficient, cos(η) is the actual power factor, and cos(φ) is the rated power factor.

[0042] In summary, the present invention provides a load monitoring and early warning method and system for an uninterruptible power supply system, including collecting the current signal of each load of the uninterruptible power supply system at the load end; monitoring all current signals, and obtaining the current peak value of each load in the current monitoring cycle based on all current signals; monitoring the system overload condition of the uninterruptible power supply system based on the current peak value of each load; setting the monitoring signal for monitoring the system overload condition in parallel with the monitoring signal originally used to monitor the load overload condition of a single device in the UPS device; and performing load monitoring and early warning on the uninterruptible power supply system based on the two monitoring signals. The present invention solves the problem that the true overall load peak value of the system cannot be obtained due to phase influence when all load cables are connected in series with a group of mutual inductors for measurement. At the same time, the overload condition of the system can be effectively monitored. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 A flow chart of a load monitoring and early warning method for an uninterruptible power supply system provided by an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of a dual-machine dual-busbar with busbar coupling operation wiring method provided in an embodiment of the present invention;

[0046] Figure 3 A schematic diagram of the phase shift phenomenon of AC power output by a UPS device provided in an embodiment of the present invention;

[0047] Figure 4 This is a schematic diagram of the system overload alarm principle provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to make the purposes, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] See also Figure 1 This embodiment provides a load monitoring and early warning method for an uninterruptible power supply system, comprising the following steps:

[0050] S100: collecting current signals of each load of the uninterruptible power supply system at the load end;

[0051] S200: monitoring all current signals, and calculating the current peak value of each load in the current monitoring period based on all current signals;

[0052] S300: Monitors the system overload of the uninterruptible power supply system based on the current peak value of each load;

[0053] S400: a monitoring signal for monitoring system overload and a monitoring signal originally used for monitoring load overload of a single device in the UPS device are connected in parallel;

[0054] S500: Provides load monitoring and early warning for the uninterruptible power supply system based on two monitoring signals.

[0055] The inventors discovered that when developing and designing their products, UPS manufacturers only considered whether the UPS device would issue corresponding alarms based on whether its own load was overloaded, but never considered whether the overall system load was overloaded.

[0056] Taking the dual-machine dual-busbar with busbar connection wiring method currently used in most substations as an example, the wiring is as follows: Figure 2 As shown in the figure. In dual-bus operation, each UPS device carries a load bus, and a bus tie switch is installed between the two bus sections. Assuming that UPS device #1 needs to be shut down due to a fault or maintenance, to prevent the load on bus section I from losing pressure, the bus tie switch K13 needs to be closed and K3 (bypass switch), K4 (maintenance bypass switch), and K5 (UPS output switch) need to be opened. At this time, both load bus sections are powered by UPS device #2. Even if the two UPS devices are operated independently, their respective loads are at a reasonable level (under normal conditions, the load power of each UPS device reaches 50% to 60% of the rated power). However, if only one UPS device is supplying power, there will be a clear overload (under normal conditions, the load will reach 100% to 120% of the rated power).

[0057] Therefore, the reason why the total load of the uninterruptible power supply system exceeds the capacity limit of a single UPS is that, in addition to the gradual increase in important loads in the substation, which exceeds the original redundancy design range of the substation, the monitoring unit of the uninterruptible power supply system does not have a load statistics function. Therefore, the monitoring unit cannot determine whether the overall load of the system exceeds the capacity of a single UPS device.

[0058] Therefore, this embodiment provides a load monitoring and early warning method for an uninterruptible power supply system, including collecting the current signal of each load of the uninterruptible power supply system at the load end; monitoring all current signals, and obtaining the current peak value of each load in the current monitoring cycle based on all current signals; monitoring the system overload condition of the uninterruptible power supply system based on the current peak value of each load; setting the monitoring signal used to monitor the system overload condition in parallel with the monitoring signal originally used to monitor the load overload condition of a single device in the UPS device; and performing load monitoring and early warning on the uninterruptible power supply system based on the two monitoring signals. The present invention can effectively and timely monitor the overload condition of the entire system by obtaining the current peak value of each load to participate in the overload monitoring calculation of the system.

[0059] In another embodiment of the present invention, the current signal of each load of the uninterruptible power supply system is collected separately at the load end. Specifically, a digital AC transformer is used at the load end to collect the current signal of each load of the uninterruptible power supply system at a set sampling frequency to obtain a current sampling signal of each load.

[0060] Under the traditional load monitoring method, the inventors found that the current UPS device still has the problem that the load is difficult to count due to the phase shift of the input and output power.

[0061] The biggest difference between the AC power input to the UPS device and the AC load output, besides the difference in voltage stabilization accuracy, lies in the AC phase. The AC power input to the UPS device is converted into a DC power supply after passing through the rectifier module, and is connected in parallel with the charger and battery of the DC system to form a reliable power supply with stable voltage and never losing voltage. Finally, it passes through the inverter module of the UPS device and is converted back into a simulated sinusoidal AC power supply. During this rectification and inversion process, the phase of the output AC power has shifted. The degree of this phase shift is different for each UPS device. Therefore, the two UPS AC outputs of the uninterruptible power supply system are very likely to have phase inconsistencies. If an AC transformer is used to simultaneously sample the current of two AC circuits with inconsistent phases, the result is the vector sum of the two currents, and the vector sum is much lower than the sum of the absolute values. The load statistics require the sum of the absolute values of the currents, so this solution is not feasible. The sampling waveform after phase shift is as follows Figure 3 shown.

[0062] Therefore, in this embodiment, since the load currents of different busbar sections have different phases, and monitoring units from all manufacturers lack the capability to sum load currents, particularly peak current summation, it is not possible to simply connect all load cables to a common set of transformers or perform secondary current sampling in parallel to achieve summation. Therefore, the first step in solving the current sampling and statistical problem is to eliminate phase effects and convert the analog current into a purely digital current value. However, considering the need to record the specific loads that generate dynamic fluctuations and their peak values, the existing UPS system transformers are no longer sufficient. Therefore, it is necessary to install a digital AC current transformer (AC / DC) with a built-in analog-to-digital converter (ADC) at each load to convert the analog current into a digital value. These transformers convert current signals into digital outputs, typically outputting data via a standard serial digital interface (such as SPI or I2C) or USB. Since the digitization process is completed internally within the transformer, no external circuitry or processor is required to convert the signal into digital form. This makes digital AC current transformers easy to use and very convenient. The analog current is converted into a digital signal via an A / D converter.

[0063] Secondly, since the UPS system only monitors the total input and output current of the UPS and does not have sampling values for each branch load, the UPS monitoring unit does not have internal calculation logic for peak value calculation. Therefore, it is necessary to fully record the current change curve of each load during load monitoring to obtain the load peak value and complete the calculation. For the calculation of the current peak value, this embodiment assumes that there is a current sampling signal with a sampling frequency of Fs and contains N sampling points. The value of each sampling point is I(i), where i is the sampling point number, from 1 to N. To calculate the maximum peak value of this current sampling signal, we can design a set of formulas according to the following steps:

[0064] 1. Calculate the mean value I_mean of the current sampling signal using the formula:

[0065] I_mean=(1 / N)*Σ(i=1to N)I(i)

[0066] 2. Subtract the mean from the value of each sampling point to obtain the deviation value I_dev(i). The formula is:

[0067] I_dev(i)=I(i)-I_mean

[0068] 3. Calculate the square of the deviation value and obtain the square of the deviation value I_dev_sq(i). The formula is:

[0069] I_dev_sq(i)=I_dev(i) 2

[0070] 4. Calculate the mean of the squared deviation values I_dev_sq_mean using the following formula:

[0071] I_dev_sq_mean=(1 / N)*Σ(i=1to N)I_dev_sq(i)

[0072] 5. Calculate the square root of I_dev_sq_mean to get the standard deviation I_std. The formula is:

[0073] I_std=sqrt(I_dev_sq_mean)

[0074] 6. Calculate the maximum peak value Y1 (the first branch, the second branch maximum peak value Y2, and so on), the formula is:

[0075] Y1=I_mean+(k*I_std)

[0076] Here, k is a coefficient that can be selected based on the specific model and operating time of the UPS device. Generally, the value of k is 2 to 4, which can ensure the accuracy of the maximum peak value to a certain extent.

[0077] In summary, the formula for calculating the maximum peak value of the current sampling value is:

[0078] Y1=I_mean+(k*sqrt((1 / N)*Σ(i=1to N)(I(i)-I_mean) 2 ))

[0079] That is, the calculation formula for the current peak is:

[0080] Y=I_ mean +(k*I_ std )

[0081] Where Y is the peak current, I_ mean is the mean value of the current sampling signal, I_ std is the standard deviation of the current sampling signal, k is the coefficient, and k∈[2,4].

[0082] In another embodiment of the present invention, the system overload condition of the uninterruptible power supply system is monitored based on the current peak value of each load, specifically:

[0083] Set the system overload threshold on the UPS device side;

[0084] Calculate the total peak current of all loads and compare it with the system overload threshold;

[0085] If it is greater than the system overload threshold, it is considered that the uninterruptible power supply system has a systematic overload or a transient overload caused by a dynamic load.

[0086] System overload threshold Y set It is the upper limit of the overall load of the UPS system. It is related to the power capacity and effective output power of the UPS system. According to the existing regulations, it is as follows:

[0087] 1. The output rated power of any of the two UPSs should be no less than 1.2 times the sum of the actual capacity of all loads to ensure that the UPS system still has 20% redundant capacity when one of the UPSs stops operating.

[0088] 2. The UPS power capacity should meet the starting current requirements of the maximum power load.

[0089] 3. The relationship between UPS power capacity (Sn) and output rated power (Pn) is: Pn (kW) = 0.8Sn (kVA). The power capacity of each UPS in substations of 500kV and above, 220kV, and 110kV and below can be selected as 10KVA, 5KVA, and 3KVA respectively.

[0090] Taking the UPS with a rated power of 3kVA and two UPS devices with two load bus power supply modes as an example, the power capacity of one UPS device is Pn (kW) = 0.8Sn (kVA) = 0.8×3 = 2.4kW. According to the requirements of the first point, the load power upper limit of the uninterruptible power supply system in the station is Pmax = 2.4kW ÷ 1.2 = 2kW, so the load current upper limit is Imax = Pmax ÷ U = 2000 ÷ 220 = 9A.

[0091] According to the above formula, the upper limit of load current of 10KVA and 5KVA capacity can be obtained as follows:

[0092] The upper limit of the total load current Yset of a 10KVA rated power UPS is 30A;

[0093] The upper limit of the total load current Yset of a 5KVA rated power UPS is 15A;

[0094] The upper limit of the total load current Yset of a 3KVA UPS is 9A.

[0095] However, considering that after a long period of operation, the UPS device may experience varying degrees of output power decline due to reasons such as component aging. In other words, the effective output power is not equal to its rated power upper limit. Therefore, it is also necessary to propose a formula correction for the effective output power:

[0096] The UPS device AC input voltage Us, DC input voltage Ul, AC input current Is, DC input current Il, as well as the AC voltage Ue and AC output current Ie after rectification and inversion are obtained through sampling.

[0097] Calculate the total input power, which can be expressed as the square root of the sum of the squares of the product of the input AC voltage and the input AC current, that is,

[0098] S1=sqrt[(Us*Is)2+(Ul*Ie) 2 ]

[0099] The output active power can be expressed as the product of the output AC voltage and the output AC current, that is, P1 = Ue * Ie

[0100] The actual power factor cos(η) of the UPS device can be expressed as

[0101] cos(η)=S1 / P1=[Ue*Ie] / {sqrt[(Us*Is) 2 +(Ul*Ie) 2 ]}

[0102] Therefore, the UPS power output correction factor δ is the difference between the actual power factor and the rated power factor. The ratio of:

[0103]

[0104] Therefore, the upper limit of load current of 10KVA and 5KVA capacity after correction is as follows:

[0105] The upper limit of the total load current Yset of a 10KVA UPS is 30*δA.

[0106] The upper limit of the total load current Yset of a 5KVA UPS is 15*δA.

[0107] The upper limit of the total station load current Yset for a 3KVA rated power UPS is: 9*δA.

[0108] That is, the system overload threshold is calculated according to the following formula:

[0109]

[0110] Where Y set is the system overload threshold, Y0 is the upper limit of the load current of the entire station, δ is the correction coefficient, cos(η) is the actual power factor, and cos(φ) is the rated power factor.

[0111] In this embodiment, it is necessary to monitor the load peak values (Y1, Y2, Y X ....), since the system may be overloaded as a whole, or the total load of different loads may be overloaded at different times, the total load Y of the system is obtained by adding up all the load peaks in a cycle. max If it exceeds the set value Y setAn alarm is issued when the system is overloaded, and the overall overload situation of the system is judged accordingly.

[0112] In another embodiment of the present invention, a monitoring signal for monitoring system overload conditions and a monitoring signal originally used to monitor the load overload conditions of a single device in a UPS device are set in parallel, and an overload alarm signal is issued when an uninterruptible power supply system is overloaded or when a single UPS device is overloaded.

[0113] In actual implementation, a load warning device can be designed on the UPS side. The human-machine interactive panel of the device can observe the load change curve, including the load current peak value on each side and the total load peak value. The current overload alarm value I can also be set through the "+", "-", "set" and other buttons set The circuit board should have a working indicator light (green), a circuit board abnormality indicator light (yellow), and a current overload alarm indicator light (red). The circuit board should have a data reset button to reset the value of each load current peak (without resetting Iset), automatically save the data, and not reset it after the circuit board is powered off and restarted.

[0114] The principle of circuit board to realize overload alarm is as follows Figure 4 As shown in the figure, Ymax>Yset is the signal trigger logic judgment contact. When the microcontroller calculates that the full load peak of the UPS system is greater than the rated capacity of the UPS system (set by maintenance personnel based on the installed capacity), this contact closes briefly. KT is the signal trigger relay. The logic judgment contact cannot remain closed for a long time. Trigger relay KT is used to withstand the current surge generated by the signal trigger. When KT is energized, it drives the contact connected by the dashed line below the relay to close, thereby energizing the signal self-latch relay KV. KV is the signal self-latch relay (bar graph), which is used to maintain the long-term output of the signal and requires KT to be activated. After activation, it drives the contact of the same name KV (switch graph) to close. When the logic judgment contact (Ymax>Yset) opens, the KT relay loses power, and the linked contact (connected by the dashed line) also opens synchronously. RESET is the reset button used to release the self-latch state of signal relay KV. When pressed, the contact opens, de-energizing the KV relay, which in turn drives the KV contact to open synchronously, thus releasing the signal.

[0115] The signal contacts of the signal relay KV can withstand an AC 220V working voltage and are independent of the circuit board's working power supply, without interfering with each other. When Ymax>Yset, the switch KV is closed, the circuit is connected, and a system overload alarm signal is issued at the load warning device end; at the same time, it should be noted that the signal relay KV is also set in parallel with another circuit switch originally used to monitor the load of a single UPS device. The signal contacts of the signal relay KV are connected in parallel with the load overload signal of the original UPS system, that is, whether there is a real-time overload of the UPS device, a systemic overload of the UPS, or a temporary overload caused by a dynamic load due to insufficient power redundancy, the signal can be triggered. When the operating personnel arrive at the site for inspection, they can view the overload records and causes through the human-computer interaction panel. After troubleshooting or migrating the load, the old data can be cleared by pressing the reset button.

[0116] The above is a detailed introduction to an embodiment of a load monitoring and early warning method for an uninterruptible power supply system of the present invention. The following is a detailed introduction to an embodiment of a load monitoring system for an uninterruptible power supply system of the present invention.

[0117] This embodiment provides a load monitoring and early warning system for an uninterruptible power supply system, including: a current acquisition unit, a signal processing unit, a system overload monitoring unit, and an early warning unit.

[0118] In this embodiment, the current acquisition unit is used to respectively acquire the current signal of each load of the uninterruptible power supply system at the load end;

[0119] In this embodiment, the signal processing unit is used to monitor all current signals and calculate the current peak value of each load in the current monitoring period based on all current signals;

[0120] In this embodiment, the system overload monitoring unit is used to monitor the system overload condition of the uninterruptible power supply system based on the current peak value of each load; wherein the monitoring signal for monitoring the system overload condition and the monitoring signal originally used to monitor the load overload condition of a single device in the UPS device are arranged in parallel;

[0121] In this embodiment, the early warning unit is used to perform load monitoring and early warning on the uninterruptible power supply system based on two monitoring signals.

[0122] Furthermore, in the current acquisition unit, the current signal of each load of the uninterruptible power supply system is collected at the load end, specifically:

[0123] A digital AC transformer is used at the load end to collect the current signal of each load of the uninterruptible power supply system according to the set sampling frequency to obtain the current sampling signal of each load.

[0124] Furthermore, in the signal processing unit, the current peak is calculated according to the following formula:

[0125] Y=I_ mean +(k*I_ std )

[0126] Where Y is the peak current, I_ mean is the mean value of the current sampling signal, I_ std is the standard deviation of the current sampling signal, k is the coefficient, and k∈[2,4].

[0127] Furthermore, in the system overload monitoring unit, the system overload condition of the uninterruptible power supply system is monitored based on the current peak value of each load, specifically:

[0128] Set the system overload threshold;

[0129] Calculate the total peak current of all loads and compare it with the system overload threshold;

[0130] If it is greater than the system overload threshold, it is considered that the uninterruptible power supply system has a systematic overload or a transient overload caused by a dynamic load.

[0131] Furthermore, in the system overload monitoring unit, the system overload threshold is calculated according to the following formula:

[0132]

[0133] Where Y set is the system overload threshold, Y0 is the upper limit of the load current of the entire station, δ is the correction coefficient, cos(η) is the actual power factor, and cos(φ) is the rated power factor.

[0134] It should be noted that the load monitoring and early warning system provided in this embodiment is used to implement the load monitoring and early warning method provided in the above embodiments. The specific settings of each unit are based on the complete implementation of the method and will not be repeated here.

[0135] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A load monitoring and early warning method for an uninterruptible power supply system, characterized in that: The steps include: Collect the current signal of each load of the uninterruptible power supply system at the load end; Monitor all current signals and calculate the current peak value of each load in the current monitoring period based on all current signals; monitoring a system overload condition of the uninterruptible power supply system based on a current peak value of each load; The monitoring signal for monitoring system overload is connected in parallel with the monitoring signal originally used to monitor the load overload of a single device in the UPS device; Load monitoring and early warning are performed on the uninterruptible power supply system based on the two monitoring signals.

2. The load monitoring and early warning method for an uninterruptible power supply system according to claim 1, characterized in that: At the load end, the current signals of each load in the uninterruptible power supply system are collected separately, specifically: A digital AC transformer is used at the load end to collect the current signal of each load of the uninterruptible power supply system according to the set sampling frequency to obtain the current sampling signal of each load.

3. The load monitoring and early warning method for an uninterruptible power supply system according to claim 2, characterized in that: The current peak value is specifically calculated according to the following formula: Y=I_ mean +(k*I_ std ) Where Y is the peak current, I_ mean is the mean value of the current sampling signal, I_ std is the standard deviation of the current sampling signal, k is the coefficient, and k∈[2,4].

4. The load monitoring and early warning method for an uninterruptible power supply system according to claim 1, characterized in that: Monitoring the system overload condition of the uninterruptible power supply system based on the current peak value of each load is specifically as follows: Set the system overload threshold; Calculating the total peak current of all loads and comparing it with the system overload threshold; If it is greater than the system overload threshold, it is considered that the uninterruptible power supply system has a systematic overload or a transient overload caused by a dynamic load.

5. The load monitoring and early warning method for an uninterruptible power supply system according to claim 4, characterized in that: The system overload threshold is calculated according to the following formula: Where Y set is the system overload threshold, Y0 is the upper limit of the load current of the entire station, δ is the correction coefficient, cos(η) is the actual power factor, and cos(φ) is the rated power factor.

6. A load monitoring and early warning system for an uninterruptible power supply system, characterized in that: include: A current acquisition unit is used to collect the current signal of each load of the uninterruptible power supply system at the load end; A signal processing unit, configured to monitor all current signals and calculate, based on the current signals, the peak current of each load within a current monitoring period; a system overload monitoring unit, configured to monitor a system overload condition of the uninterruptible power supply system based on the current peak value of each load; wherein a monitoring signal for monitoring the system overload condition and a monitoring signal originally used in the UPS device to monitor the load overload condition of a single device are arranged in parallel; An early warning unit is used to perform load monitoring and early warning on the uninterruptible power supply system based on the two monitoring signals.

7. The load monitoring and early warning system for an uninterruptible power supply system according to claim 6, characterized in that: In the current acquisition unit, the current signal of each load of the uninterruptible power supply system is collected at the load end, specifically: A digital AC transformer is used at the load end to collect the current signal of each load of the uninterruptible power supply system according to the set sampling frequency to obtain the current sampling signal of each load.

8. The load monitoring and early warning system for an uninterruptible power supply system according to claim 7, characterized in that: In the signal processing unit, the current peak is calculated according to the following formula: Y=I_ mean +(k*I_ std ) Where Y is the peak current, I_ mean is the mean value of the current sampling signal, I_ std is the standard deviation of the current sampling signal, k is the coefficient, and k∈[2,4].

9. The load monitoring and early warning system for an uninterruptible power supply system according to claim 6, characterized in that: In the system overload monitoring unit, the system overload condition of the uninterruptible power supply system is monitored based on the current peak value of each load, specifically: Set the system overload threshold; Calculating the total peak current of all loads and comparing it with the system overload threshold; If it is greater than the system overload threshold, it is considered that the uninterruptible power supply system has a systematic overload or a transient overload caused by a dynamic load.

10. The load monitoring and early warning system for an uninterruptible power supply system according to claim 9, characterized in that: In the system overload monitoring unit, the system overload threshold is calculated specifically according to the following formula: Where Y set is the system overload threshold, Y0 is the upper limit of the load current of the entire station, δ is the correction coefficient, cos(η) is the actual power factor, and cos(φ) is the rated power factor.

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