Inverter constant power output control method and inverter

Abstract

The invention provides an inverter constant power output control method and an inverter. The control method comprises the following steps: acquiring the current output power of the inverter in real time according to a preset adjustment period; calculating a difference value between the current output power and a preset target constant power to obtain a power deviation; when the power deviation is greater than a preset deviation threshold value, selecting a corresponding voltage regulation step length according to a preset numerical value interval in which the size of the power deviation is located; wherein the deviation threshold value is greater than or equal to zero, and the voltage regulation step length is in positive correlation with the power deviation; and reducing the output voltage of the inverter according to the selected voltage regulation step length. According to the constant power output control method for the inverter, the inverter can be effectively prevented from being overloaded, and common electric appliances with the power slightly higher than the nominal value of the inverter can continue to work at a low power level through accurate regulation and control, so that the availability of basic functions and the continuity of power supply are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of inverter technology, and in particular to a constant power output control method for an inverter and an inverter. Background Technology

[0002] An inverter is a power electronic device that converts direct current (DC) to alternating current (AC). It is widely used in solar power generation, energy storage systems, outdoor power supplies, and uninterruptible power supplies (UPS). In practical applications, the power of the load connected to the inverter often changes dynamically.

[0003] Especially for products such as outdoor energy storage power supplies, the maximum output power of their core component, the inverter, is usually limited (e.g., rated power of 2000W). However, in actual use, users may connect resistive loads with a rated power slightly greater than the inverter's rated value, such as an electric kettle with a rated power of 2400W.

[0004] In response to the above situation, existing control strategies mainly have the following two approaches and their corresponding drawbacks: The first type is the traditional overload protection scheme. Under this strategy, once the inverter detects that the connected load power exceeds its rated value, it will directly activate the protection mechanism and cut off the output due to overload. Although this "one-size-fits-all" protection method can protect the equipment from damage, it directly leads to a power outage, sacrifices the availability of functions, and results in a very poor user experience.

[0005] The second approach is a linear buck converter with a fixed power limit. This approach attempts to linearly reduce the output voltage when the power exceeds a threshold. However, this method has the disadvantage of a slow response time and is prone to large power overshoot or oscillations when the load changes drastically, resulting in poor system stability and potentially causing the load (such as the heating element of a kettle) to operate in an unstable state.

[0006] Therefore, it is necessary to study the constant power output of inverters. Summary of the Invention

[0007] The purpose of this invention is to solve the above-mentioned technical problems by providing a constant power output control method and inverter for inverters that can effectively prevent inverter overload and enable commonly used electrical appliances with power slightly exceeding the inverter's nominal value to continue working at a lower power level through precise control.

[0008] To achieve the above objectives, the present invention provides a constant power output control method for an inverter, comprising: The inverter's current output power is obtained in real time according to the preset adjustment cycle; Calculate the difference between the current output power and the preset target constant power to obtain the power deviation; When the power deviation is greater than a preset deviation threshold, a corresponding voltage adjustment step size is selected according to the preset value range in which the power deviation falls; wherein, the deviation threshold is greater than or equal to zero, and the voltage adjustment step size is positively correlated with the power deviation; The inverter's output voltage is lowered according to the selected voltage adjustment step size.

[0009] Preferably, the adjustment period is an integer multiple of the inverter's power frequency period.

[0010] Preferably, the method for obtaining the current output power of the inverter in real time according to a preset adjustment period includes: According to the preset detection frequency, the instantaneous output voltage and instantaneous output current of the inverter are collected multiple times in each power frequency cycle of the inverter; The instantaneous power is calculated based on the instantaneous output voltage and instantaneous output current collected each time. The current output power is obtained by accumulating and averaging all instantaneous power within one or more of the aforementioned power frequency cycles.

[0011] Preferably, the method for reducing the output power of the inverter according to the selected voltage regulation step size includes: The voltage reference value corresponding to the output voltage of the inverter is reduced according to the selected voltage regulation step size, and a pulse width modulation signal is generated using the updated voltage reference value to drive the inverter to operate, thereby reducing the output voltage of the inverter.

[0012] Preferably, methods for reducing the voltage reference value of the inverter corresponding to the output voltage include: The selected voltage adjustment step size is subtracted from the voltage reference value determined in the previous adjustment cycle to obtain the voltage reference value for the current adjustment cycle.

[0013] Preferably, before generating the pulse width modulation signal using the updated voltage reference value, the method further includes: Determine whether the updated voltage reference value is less than a preset minimum voltage protection threshold. If so, correct the voltage reference value to the minimum voltage protection threshold and generate a pulse width modulation signal using the corrected voltage reference value.

[0014] Preferably, the deviation threshold is taken as 1% to 5% of the target constant power.

[0015] The present invention also provides an inverter, which includes a controller and a power module, wherein the controller controls the output power of the power module based on the inverter constant power output control method described above.

[0016] The present invention also provides a constant power output control system for an inverter, comprising: One or more processors; Memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including instructions for performing the inverter constant power output control method as described above.

[0017] The present invention also provides a computer-readable storage medium comprising a computer program that can be executed by a processor to perform the inverter constant power output control method as described above.

[0018] Compared with existing technologies, the inverter constant power output control method provided by the above technical solution selects a corresponding voltage adjustment step size to adjust the inverter's output voltage based on the preset value range of the power deviation. This segmented variable step size adjustment strategy solves the contradiction of traditional fixed step size adjustment. When the power deviation is large, a larger voltage adjustment step size is selected, which can quickly reduce the voltage and bring the power back to the safe range, achieving rapid response. When the power deviation is small, the system selects a smaller voltage adjustment step size for fine adjustment, avoiding power overshoot or oscillation caused by excessive adjustment amplitude, thus ensuring the stability of the control process. Secondly, this solution reduces the output power by actively lowering the output voltage, allowing the inverter to continue operating under a power limit (target constant power) state. This means that when a user connects a slightly larger power load, the equipment will not suddenly lose power, but will maintain a derating operation state, thereby ensuring the availability of service functions and the continuity of power supply. Attached Figure Description

[0019] Figure 1 This is a flowchart of the inverter constant power output control method in an embodiment of the present invention. Detailed Implementation

[0020] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0021] This embodiment discloses a constant power output control method for an inverter. The inverter in this method is mainly used in outdoor energy storage power supplies or uninterruptible power supplies (UPS) and other equipment. It is used to maintain the inverter at a constant target power output when the load power exceeds the inverter's rated power, so as to avoid equipment overload shutdown.

[0022] So, if Figure 1 The specific execution process of this control method is as follows: S1: Obtain the current output power of the inverter in real time according to the preset adjustment cycle.

[0023] For example, with a preset adjustment period of 20ms, the inverter controller samples the output voltage and output current every 20ms and calculates the current actual output power. Suppose that at a certain moment T1, the user connects a hair dryer with a high rated power, and the controller detects that the current output power Pc rises sharply to 2300W.

[0024] S2: Calculate the difference between the current output power and the preset target constant power to obtain the power deviation.

[0025] In this embodiment, the inverter's preset target constant power Pt (i.e., rated power) is 2000W. The controller internally calculates the difference between the current output power and the target constant power: ΔP=Pc Pt=2300W 2000W = 300W.

[0026] That is, the current power deviation is 300W.

[0027] S3: Determine whether the power deviation is greater than the preset deviation threshold. If yes, proceed to S4; otherwise, proceed to S6.

[0028] In this embodiment, the preset deviation threshold is 10W.

[0029] In this embodiment, the controller determines whether the power deviation ΔP (300W) is greater than the preset deviation threshold (10W). Obviously, 300W > 10W, which satisfies the adjustment condition.

[0030] S4: Select the corresponding voltage adjustment step size according to the preset value range of the power deviation.

[0031] The controller selects the voltage regulation step size based on a pre-stored "deviation-step mapping table".

[0032] In this embodiment, the correspondence between the preset numerical range and the voltage adjustment step size is as follows: Range A (slight overload): When 10W < ΔP ≤ 100W, the voltage adjustment step Vstep = 0.5V; Range B (moderate overload): When 100W < ΔP ≤ 250W, the voltage adjustment step size Vstep = 1.5V; Range C (severe overload): When ΔP>250W, the voltage adjustment step Vstep=3.0V.

[0033] Since the current power deviation is 300W, which falls within the range of C (severe overload), the controller selects a larger voltage regulation step size, i.e., Vstep=3.0V.

[0034] S5: Adjust the inverter's output voltage according to the selected voltage adjustment step size, and return to S1. Assuming the inverter's current output voltage (RMS value) is 220V, the controller will perform a step-down operation according to the selected step size: Vnew=Vold Vstep=220V 3.0V = 217V.

[0035] The controller updates the inverter's output voltage to 217V and adjusts the PWM drive signal accordingly.

[0036] Step S6: Keep the current output voltage of the inverter unchanged and return to S1.

[0037] In the next adjustment cycle T2 (20ms later), the output power will decrease accordingly as the voltage has decreased.

[0038] Suppose that the current output power is measured to be 2150W at time T2.

[0039] At this point, the power deviation ΔP = 150W.

[0040] If the deviation falls into interval B (moderate overload), the controller will select a smaller step size Vstep = 1.5V.

[0041] The new output voltage will then be adjusted to: 217V 1.5V = 215.5V.

[0042] Through the above cyclical adjustment, as the power deviation decreases, the voltage adjustment step size also decreases (from 3.0V to 1.5V, and then to 0.5V), achieving the control effect of "large step size for large deviation and small step size for small deviation" until the output power stabilizes at 2000W (or slightly higher than 2000W but within the allowable deviation range), thereby maintaining the load operation while ensuring no overload.

[0043] The above control method adjusts the inverter's output voltage by selecting a corresponding voltage adjustment step size based on the preset value range of the power deviation. This segmented variable step size adjustment strategy resolves the contradictions of traditional fixed step size adjustment.

[0044] When the power deviation is large, a larger voltage adjustment step size is selected, which can quickly reduce the voltage and bring the power back to the safe range, thus achieving a fast response. When the power deviation is small, the system selects a smaller voltage adjustment step size for fine adjustment, avoiding power overshoot or oscillation caused by excessive adjustment amplitude, thereby ensuring the stability of the control process.

[0045] Secondly, this solution reduces output power by actively lowering the output voltage, allowing the inverter to continue operating under limited power (target constant power). This means that when a user connects a slightly larger power load, the device will not suddenly lose power, but will remain in a derating state, thus ensuring the availability of service functions and the continuity of power supply.

[0046] On the other hand, the deviation threshold is set at 1% to 5% of the target constant power.

[0047] For example, for an inverter with a target constant power setting of 2000W, in order to achieve high-precision power output, the user or factory settings may set the deviation threshold to 1% of the target power.

[0048] Therefore, the deviation threshold = 2000W × 1% = 20W.

[0049] On the other hand, the adjustment period is an integer multiple of the inverter's power frequency period.

[0050] Specifically, the method for obtaining the current output power of the inverter in real time according to a preset adjustment cycle includes: According to the preset detection frequency, the instantaneous output voltage and instantaneous output current of the inverter are collected multiple times in each power frequency cycle of the inverter; Calculate the instantaneous power based on the instantaneous output voltage and instantaneous output current collected each time; The current output power is obtained by summing up and averaging all instantaneous power within one or more power frequency cycles.

[0051] In this embodiment, the inverter output is a standard sinusoidal alternating current, with an output frequency set to 50Hz. According to physical principles, the single power frequency cycle Tac of this inverter is: Tac = 1 / f = 1 / 50Hz = 0.02s = 20ms.

[0052] The controller sets the preset adjustment period Tad to an integer multiple of the power frequency period, i.e., Tad = N × Tac (where N is a positive integer).

[0053] If N=1 is set, the adjustment period is 20ms.

[0054] The controller monitors the inverter's output voltage via a zero-crossing detection circuit. Each time a zero-crossing is detected, a new sampling and calculation cycle begins. The controller integrates the voltage and current over a full 20ms period to calculate the average active power within that cycle.

[0055] This configuration allows the system to respond to load changes at the fastest speed (cycle-by-cycle), making it suitable for applications with extremely high overload protection response speed requirements.

[0056] Alternatively, N can be set to other positive integers, such as N=5, which means the adjustment period is 100ms. Then, the controller continuously collects voltage and current data over 5 power frequency cycles and calculates the average power over these 5 cycles as the "current output power".

[0057] Therefore, the controller executes the above adjustment logic once every 100ms. This setting can effectively filter out the interference caused by instantaneous load fluctuations (such as the spike at the moment of motor start-up) and avoid frequent voltage jumps caused by sampling fluctuations in a single cycle. It is suitable for application scenarios with large load fluctuations but high requirements for adjustment smoothness.

[0058] By locking the adjustment period to an integer multiple of the power frequency period, this embodiment ensures that a complete sine wave is used in each calculation, thereby guaranteeing the accuracy of the power calculation value and providing an accurate data basis for subsequent voltage step selection.

[0059] On the other hand, methods for reducing the inverter's output power based on the selected voltage regulation step size include: The inverter's voltage reference value corresponding to the output voltage is reduced according to the selected voltage regulation step size, and a pulse width modulation signal is generated using the updated voltage reference value to drive the inverter to operate, thereby reducing the inverter's output voltage.

[0060] In addition, the selected voltage adjustment step size is subtracted from the voltage reference value determined in the previous adjustment cycle to obtain the voltage reference value for the current adjustment cycle.

[0061] Specifically, the inverter's digital controller (such as a DSP or MCU) stores a variable used to control the output voltage amplitude, known as the "voltage reference value" (denoted as Vref). This variable determines the effective value of the inverter's desired output voltage.

[0062] Assuming in the current adjustment cycle In the middle, the controller has already selected a voltage regulation step size based on the magnitude of the power deviation. .

[0063] The controller reads the previous adjustment cycle. The determined voltage reference value Assume that in the previous adjustment cycle, the inverter was operating at a standard 220V output.

[0064] The controller then updates the voltage reference value for the current cycle based on the voltage adjustment step size. .

[0065] At this point, the voltage control target inside the controller has changed from 220V to 218V. It should be noted that this is an iterative update process; if the voltage needs to be reduced again in the next cycle, the new step size will be subtracted from the 218V base.

[0066] After obtaining the updated voltage reference value, the controller needs to convert it into physical signals to control the switching transistors of the inverter circuit. The specific process is as follows: First, the controller utilizes the updated As the amplitude coefficient, a standard sinusoidal modulation wave is generated, and an SPWM (sinusoidal pulse width modulation) signal is generated accordingly.

[0067] Through the above process, this embodiment accurately performs step-based voltage reduction operation, ensuring that the inverter can smoothly and accurately reduce output power.

[0068] On the other hand, before generating the pulse width modulation signal using the updated voltage reference value, the process also includes: Determine whether the updated voltage reference value is less than the preset minimum voltage protection threshold. If so, correct the voltage reference value to the minimum voltage protection threshold and generate a pulse width modulation signal using the corrected voltage reference value.

[0069] Based on this, the inverter system avoids the output voltage from "returning to zero" or dropping to an uncontrollable range due to unlimited voltage reduction. Even under extreme overload conditions, the inverter can maintain operation at the minimum safe voltage, achieving both power limiting and ensuring the basic operational stability of the system, preventing secondary faults caused by excessively low voltage.

[0070] In another preferred embodiment of the present invention, an inverter is also disclosed, which includes a controller and a power module, wherein the controller controls the output power of the power module based on the inverter constant power output control method in the above embodiment.

[0071] This invention also discloses a constant power output control system for an inverter, comprising one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors. The programs include instructions for performing the constant power output control method as described above. The processor may be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, used to execute the relevant programs to implement the functions required by the modules in the constant power output control system of this application embodiment, or to execute the constant power output control method of the method embodiment of this application.

[0072] This invention also discloses a computer-readable storage medium comprising a computer program executable by a processor to perform the constant power output control method described above. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center integrating one or more available media. The available medium can be read-only memory (ROM), random access memory (RAM), or magnetic media, such as floppy disks, hard disks, magnetic tapes, magnetic disks, or optical media, such as digital versatile discs (DVDs), or semiconductor media, such as solid-state disks (SSDs).

[0073] This application also discloses a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. The processor of an electronic device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the electronic device to perform the aforementioned constant power output control method.

[0074] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A constant power output control method for an inverter, characterized in that, include: The inverter's current output power is obtained in real time according to the preset adjustment cycle; Calculate the difference between the current output power and the preset target constant power to obtain the power deviation; When the power deviation is greater than a preset deviation threshold, a corresponding voltage adjustment step size is selected according to the preset value range in which the power deviation falls; wherein, the deviation threshold is greater than or equal to zero, and the voltage adjustment step size is positively correlated with the power deviation; The inverter's output voltage is lowered according to the selected voltage adjustment step size.

2. The inverter constant power output control method according to claim 1, characterized in that, The adjustment period is an integer multiple of the inverter's power frequency period.

3. The inverter constant power output control method according to claim 2, characterized in that, The method for obtaining the current output power of the inverter in real time according to a preset adjustment period includes: According to the preset detection frequency, the instantaneous output voltage and instantaneous output current of the inverter are collected multiple times in each power frequency cycle of the inverter; The instantaneous power is calculated based on the instantaneous output voltage and instantaneous output current collected each time. The current output power is obtained by accumulating and averaging all instantaneous power within one or more of the power frequency cycles.

4. The inverter constant power output control method according to claim 1, characterized in that, The method for reducing the output power of the inverter according to the selected voltage regulation step size includes: The voltage reference value corresponding to the output voltage of the inverter is reduced according to the selected voltage regulation step size, and a pulse width modulation signal is generated using the updated voltage reference value to drive the inverter to operate, thereby reducing the output voltage of the inverter.

5. The inverter constant power output control method according to claim 4, characterized in that, Methods to reduce the voltage reference value of the inverter corresponding to the output voltage include: The selected voltage adjustment step size is subtracted from the voltage reference value determined in the previous adjustment cycle to obtain the voltage reference value for the current adjustment cycle.

6. The inverter constant power output control method according to claim 4, characterized in that, Before generating the pulse width modulation signal using the updated voltage reference value, the method further includes: Determine whether the updated voltage reference value is less than a preset minimum voltage protection threshold. If so, correct the voltage reference value to the minimum voltage protection threshold and generate a pulse width modulation signal using the corrected voltage reference value.

7. The inverter constant power output control method according to claim 1, characterized in that, The deviation threshold is set at 1% to 5% of the target constant power.

8. An inverter, characterized in that, It includes a controller and a power module, wherein the controller controls the output power of the power module based on the inverter constant power output control method according to any one of claims 1 to 7.

9. A constant power output control system for an inverter, characterized in that, include: One or more processors; Memory; And one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including instructions for performing the inverter constant power output control method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, Includes a computer program that can be executed by a processor to perform the inverter constant power output control method as described in any one of claims 1 to 7.

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