Method for compensating inductance current reference value, inverter and storage medium

Abstract

The application relates to the technical field of micro-grid, in particular to a method for compensating an inductance current reference value, an inverter and a storage medium. The method comprises the following steps: establishing a state equation of an inverter circuit; determining an inductance current reference value compensation model and constructing a disturbance observer for estimating unknown disturbance according to the state equation; obtaining an output voltage reference value, an inductance current sample value and an output voltage sample value, performing voltage outer loop control on the inverter to obtain an original inductance current reference value; inputting the inductance current sample value and the output voltage sample value into the disturbance observer to obtain an estimated value of the unknown disturbance; and obtaining a compensated inductance current reference value based on the original inductance current reference value, the estimated value of the unknown disturbance and the inductance current reference value compensation model. The method compensates the inductance current reference value, and realizes the purpose of optimizing the output voltage waveform quality when a single-phase off-grid inverter carries a nonlinear load.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-grid, and particularly relates to a method for compensating an inductance current reference value, an inverter and a storage medium. BACKGROUND

[0002] Single-phase off-grid inverters are widely used in the technical field of micro-grid, such as Figure 1 As shown in the figure, a common single-phase off-grid inverter is composed of four full-bridge switching tubes and a filter circuit. At present, a common control scheme for the single-phase off-grid inverter is a double-loop control strategy of an output voltage outer loop and an inductance current inner loop. However, under the double-loop control framework, when the single-phase off-grid inverter is loaded with a nonlinear load, the harmonic components in the output current will have an adverse effect on the waveform quality of the output voltage of the inverter, resulting in a poor total harmonic distortion (THD) index of the output voltage of the inverter. SUMMARY

[0003] Embodiments of the present application aim to provide a method for compensating an inductance current reference value, an inverter and a storage medium, and solve the technical problem of a large THD of the output voltage of the single-phase off-grid inverter when loaded with a nonlinear load in the prior art.

[0004] To solve the above technical problem, embodiments of the present application provide the following technical solutions:

[0005] According to a first aspect of the present application, a method for compensating an inductance current reference value is provided, the method is applied to a single-phase off-grid inverter, and includes the following steps:

[0006] establishing a state equation of an inverter circuit according to Kirchhoff's law;

[0007] determining an inductance current reference value compensation model containing an unknown disturbance quantity according to the state equation of the inverter circuit;

[0008] constructing a disturbance observer for estimating the unknown disturbance quantity according to the state equation of the inverter circuit;

[0009] obtaining an output voltage reference value, an inductance current sample value and an output voltage sample value, performing voltage outer loop control on the inverter based on the output voltage sample value and the output voltage reference value, and obtaining an original inductance current reference value;

[0010] inputting the inductance current sample value and the output voltage sample value into the disturbance observer to obtain an estimated value of the unknown disturbance quantity;

[0011] obtaining a compensated inductance current reference value based on the original inductance current reference value, the estimated value of the unknown disturbance quantity and the inductance current reference value compensation model.

[0012] Optionally, the state equation of the inverter circuit is:

[0013]

[0014] wherein, is a capacitance value of a filter capacitor, is an inductor current, is a capacitor current, is an output current, is an output voltage.

[0015] Optionally, the inductor current reference value compensation model is:

[0016]

[0017] wherein, is a compensated inductor current reference value, is an original inductor current reference value output by a voltage outer loop controller, is an estimated value of an unknown disturbance.

[0018] Optionally, the unknown disturbance is a load current.

[0019] Optionally, the obtaining of the compensated inductor current reference value based on the original inductor current reference value, the estimated value of the unknown disturbance and the inductor current reference value compensation model comprises:

[0020] superimposing the original inductor current reference value and the estimated value of the unknown disturbance to obtain the compensated inductor current reference value.

[0021] Optionally, the disturbance observer is:

[0022]

[0023] wherein, is an estimated value of an output voltage, is an inductor current sample value, is an estimated value of an unknown disturbance, and is an observer coefficient.

[0024] Optionally, the obtaining of the estimated value of the unknown disturbance based on the inductor current sample value, the output voltage sample value and the disturbance observer comprises:

[0025] discretizing the disturbance observer to obtain a discretized disturbance observer as follows, wherein, is a control period:

[0026]

[0027] initializing an estimated value of an output voltage and an estimated value of an unknown disturbance quantity in the discretized disturbance observer;

[0028] inputting the inductor current sample value and the output voltage sample value into the discretized disturbance observer to obtain an estimated value of the unknown disturbance quantity in a current control period.

[0029] According to a second aspect of the present application, a single-phase off-grid inverter is provided, the single-phase off-grid inverter comprising a controller, the controller comprising at least one processor and a memory communicatively connected to the at least one processor, the memory storing instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method of any one of the preceding aspects.

[0030] Optionally, the single-phase off-grid inverter further comprises a direct-current voltage input source, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a filter inductor and a filter capacitor.

[0031] According to a third aspect of the present application, a computer-readable storage medium is provided, the computer-readable storage medium storing a computer program, when the computer program is executed by a processor, the processor performs the steps of the method of any one of the preceding aspects.

[0032] The beneficial effects of the embodiments of the present application are as follows: Different from the prior art, in the embodiments of the present application, a method for compensating an inductor current reference value is provided, a state equation of an inverter circuit is first established, and based on the state equation of the inverter circuit, an inductor current reference value compensation model containing an unknown disturbance quantity is determined, and a disturbance observer for estimating the unknown disturbance quantity is constructed; then, an output voltage reference value, an inductor current sample value and an output voltage sample value are obtained, voltage outer loop control of the inverter is performed based on the output voltage sample value and the output voltage reference value, to obtain an original inductor current reference value, the inductor current sample value and the output voltage sample value are input into the disturbance observer to obtain an estimated value of the unknown disturbance quantity; finally, based on the original inductor current reference value, the estimated value of the unknown disturbance quantity and the inductor current reference value compensation model, a compensated inductor current reference value is obtained. In the method of the present application, after the disturbance observer estimates the disturbance quantity, the inductor current reference value is compensated based on the estimated value of the disturbance quantity, and the compensated inductor current reference value is taken as the final inductor current reference value and is sent into a current control inner loop to generate a modulation wave, so that when the inverter is loaded with a nonlinear load, the purpose of suppressing the disturbance of the load current on the output voltage and optimizing the output voltage waveform quality is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0033] One or more embodiments are illustrated by way of example in the drawings and are described herein in connection with the embodiments presented. The embodiments disclosed herein are not intended to be exhaustive or to limit the claims to the precise form disclosed. The drawings are not necessarily to scale, and in some instances, proportions have been exaggerated in order to clearly understand one or more embodiments. Like numbers in different figures represent the same, similar, or equivalent elements.

[0034] Figure 1 is a structural schematic diagram of a single-phase off-grid inverter provided by an embodiment of the present application;

[0035] Figure 2 is a structural schematic diagram of a controller provided by an embodiment of the present application;

[0036] Figure 3 is a flowchart of a method for compensating an inductor current reference value provided by an embodiment of the present application;

[0037] Figure 4 is a schematic diagram of a conventional double-closed-loop control strategy provided by an embodiment of the present application;

[0038] Figure 5 is a schematic diagram of an inductor current reference value compensation control strategy provided by an embodiment of the present application;

[0039] Figure 6 is a control effect comparison diagram of the conventional double-closed-loop control strategy and the inductor current reference value compensation control strategy provided by an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0041] In addition, the technical features involved in each of the embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0042] It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a group of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown herein.

[0043] Please refer to Figure 1 , Figure 1 is a structural schematic diagram of a single-phase off-grid inverter provided by an embodiment of the present application. As shown in Figure 1As shown, the single-phase off-grid inverter comprises an inverter circuit 10 and a controller 20. The inverter circuit 10 comprises a direct-current voltage input source, a first switch tube , a second switch tube , a third switch tube , a fourth switch tube , a filter inductor , and a filter capacitor . In addition, the single-phase off-grid inverter carries a nonlinear load Z, and the inverter bridge arm output voltage is represented as .

[0044] The controller 20 is connected with the switch tubes in the inverter circuit 10 respectively, and controls the turn-on and turn-off of the switch tubes based on the built-in control program. In some embodiments, the controller 20 can adopt a microcontroller unit (MCU) or a digital signal processing (DSP) controller, etc.

[0045] In some embodiments, the single-phase off-grid inverter can further comprise an output voltage sampling unit and an inductor current sampling unit. The output voltage sampling unit is arranged on both sides of the nonlinear load Z, for real-time acquisition of the output voltage ; the inductor current sampling unit is arranged on the inflow side of the filter inductor , for real-time acquisition of the filter inductor current .

[0046] Please refer to Figure 2 , Figure 2 for an exemplary structure of the controller 20. As shown, Figure 2 the controller 20 comprises at least one processor 21 and a memory 22, wherein the memory 22 can be built-in in the controller 20, or can be externally arranged outside the controller 20, and the memory 22 can also be a remotely arranged memory, which is connected with the controller 20 through a network.

[0047] The memory 22, as a non-volatile computer readable storage medium, can be used to store non-volatile software programs, non-volatile computer executable programs and modules. The memory 22 can include a program storage area and a data storage area, wherein the program storage area can store an operating system and at least one application required by a function; and the data storage area can store data created according to the use of the terminal and the like. In addition, the memory 22 can include a high-speed random access memory, and can also include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state memory device. In some embodiments, the memory 22 can optionally include a memory remotely arranged with respect to the processor 21, and these remote memories can be connected to the terminal through a network. Examples of the above network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0048] The processor 21 performs various functions of the terminal and processes data by running or executing software programs and / or modules stored in the memory 22 and calling data stored in the memory 22, thereby performing overall monitoring of the terminal, such as implementing the method for compensating the inductance current reference value according to any embodiment of the present application.

[0049] The processor 21 can be one or more, Figure 2 The processor 21 is taken as an example. The processor 21 and the memory 22 can be connected through a bus or other means. The processor 21 can include a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, etc. The processor 21 can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration.

[0050] Please refer to Figure 3 , Figure 3 is a flowchart of a method for compensating an inductance current reference value provided by an embodiment of the present application, and the method is applied to a single-phase off-grid inverter. The single-phase off-grid inverter can include an inverter circuit and a controller, etc. In some embodiments, the single-phase off-grid inverter can be implemented through Figure 1 , and the specific implementation process has been described in detail in the above embodiments, which will not be described here.

[0051] As shown in Figure 3 , the method for compensating the inductance current reference value includes:

[0052] In step S301, according to the Kirchhoff's law, a state equation of the inverter circuit is established.

[0053] According to the Kirchhoff's current law: the total current flowing into a node is equal to the total current flowing out of the node, then:

[0054] (1)

[0055] wherein, is the capacitance value of the filter capacitor, is the inductor current, is the capacitor current, is the output current, is the output voltage.

[0056] In step S302, the inductor current reference value compensation model containing unknown disturbance is determined according to the state equation of the inverter circuit.

[0057] The original inductor current reference value output by the voltage outer loop controller is essentially to provide the capacitor current to maintain the sinusoidal output voltage . However, when the load current contains harmonic components, in order to maintain the stability of the output voltage, the inductor current must be able to compensate for the change of the load current , that is, the inductor current needs to be able to perfectly support the capacitor current and the load current . Therefore, according to formula (1), the ideal inductor current reference value should be:

[0058] (2)

[0059] wherein, is the original inductor current reference value output by the voltage outer loop controller, used to maintain the stability of the sinusoidal output voltage , is the compensation current (i.e. the load current) needed to respond to the load current disturbance. In order to reduce the hardware cost, a current sensor is usually not added at the load end, and the load current cannot be measured in real time, therefore, the disturbance observer is introduced in the present application to estimate the load current, and the estimated load current is superimposed on the output of the voltage outer loop controller for feedforward compensation. At this time, the inductor current reference value compensation model containing unknown disturbance is:

[0060] (3)

[0061] wherein, is the compensated inductor current reference value, is the original inductor current reference value output by the voltage outer loop controller, is the estimated value of the unknown disturbance.

[0062] From the inductance current reference compensation model, the compensated inductance current reference value contains two parts: one part is the capacitor current component output by the voltage outer loop for maintaining the output voltage , and the other part is the feedforward load current estimation value . In this way, the inductance current can directly provide the load current , thereby suppressing the disturbance of the output voltage variation.

[0063] In step S303, a disturbance observer for estimating the unknown disturbance quantity is constructed according to the state equation of the inverter circuit.

[0064] According to formula (1), the state equation of the inverter circuit can be rewritten as follows:

[0065] (4)

[0066] For the unknown disturbance quantity in formula (4), a disturbance observer is constructed as follows to estimate it:

[0067] (5)

[0068] wherein is the estimated value of the output voltage, is the inductance current sample value, is the estimated value of the unknown disturbance quantity, and are observer coefficients.

[0069] In step S304, the output voltage reference value, the inductance current sample value and the output voltage sample value are obtained, the voltage outer loop control of the inverter is performed based on the output voltage sample value and the output voltage reference value, and the original inductance current reference value is obtained.

[0070] The double closed loop control strategy of the single-phase off-grid inverter includes voltage outer loop control and current inner loop control, and the control target is to make the output voltage as much as possible to track the output voltage reference value in the voltage outer loop control, and make the inductance current as much as possible to track the inductance current reference value in the current inner loop control. Specifically, the execution process of the conventional double closed loop control strategy is as follows: the voltage outer loop control is performed based on the output voltage sample value and the output voltage reference value, and the inductance current reference value is output; then the current inner loop control is performed based on the inductance current sample value and the inductance current reference value, and the modulation wave signal is output. ​

[0071] Please refer to Figure 4 This is a schematic diagram of a conventional dual-closed-loop control strategy applied to a single-phase off-grid inverter, as provided in an embodiment of this application. Figure 4 As shown, the output voltage reference value With output voltage sampling value The difference is then fed into the outer voltage loop controller. Generate inductor current reference value Inductor current reference value Then compared with the inductor current sampling value The difference is then fed into the inner current loop controller. The modulated wave signal is obtained. This modulated wave signal is then fed into a PWM (Pulse Width Modulation) modulator for modulation. Figure 4 The approximation is The proportion adjustment, among which The amplitude of the triangular carrier wave. (DC input voltage), to obtain the inverter bridge arm output voltage. Inverter bridge arm output voltage With output voltage sampling value The voltage of the filter inductor is obtained by subtraction. Filter inductor voltage With filter inductor reactance Divide to obtain the sampled value of the inductor current. Inductor current sampling value With output current The difference is used to obtain the capacitor current. Capacitor current With capacitor reactance Multiply to obtain the output voltage. .

[0072] Step S305: Input the inductor current sampling value and the output voltage sampling value into the disturbance observer to obtain the estimated value of the unknown disturbance.

[0073] Specifically, the perturbation observer in equation (5) is discretized to obtain the following discretized perturbation observer:

[0074] (6)

[0075] in, To control the cycle.

[0076] Furthermore, the estimated values ​​of the output voltage and the unknown disturbance are initialized in the discretized disturbance observer. The sampled values ​​of the inductor current and the output voltage are input into the discretized disturbance observer for recursive calculation to obtain the estimated value of the unknown disturbance for the current control cycle. Specifically, the estimated value of the unknown disturbance at time 0 is calculated in the discretized disturbance observer. and time 0 After initialization, the inductor current sample value at time 1 is obtained. and the output voltage sample value at time 1 The inductor current sample value at time 1 and the output voltage sample value at time 1 By inputting the disturbance observer into equation (6), an estimate of the output voltage at time 1 can be obtained. And the estimated value of the unknown disturbance at time 1. By recursively calculating in this way, the estimated value of the output voltage and the estimated value of the unknown disturbance can be obtained for each control cycle.

[0077] Step S306: Based on the original inductor current reference value, the estimated value of the unknown disturbance, and the inductor current reference value compensation model, the compensated inductor current reference value is obtained.

[0078] After obtaining the estimated value of the unknown disturbance in the current control cycle based on step S305, the compensated inductor current reference value is obtained based on the original inductor current reference value, the estimated value of the unknown disturbance, and the inductor current reference value compensation model of equation (3). In one embodiment, the unknown disturbance is the load current. The compensated inductor current reference value is obtained by superimposing the original inductor current reference value and the estimated value of the unknown disturbance.

[0079] Please refer to Figure 5 , Figure 5 This is a schematic diagram of the inductor current reference value compensation control strategy provided in an embodiment of this application. Figure 4 Compared to conventional dual-closed-loop control strategies, the inductor current reference value compensation control strategy of this application has a higher output voltage reference value. With output voltage sampling value The difference is then fed into the outer voltage loop controller. This generates the original inductor current reference value; the inductor current sample value is then... and output voltage sampling value The data is fed into the disturbance observer, which outputs an estimate of the unknown disturbance. Then, the original inductor current reference value and the estimated value of the unknown disturbance are used. The superposition yields the compensated inductor current reference value. Then, the compensated inductor current reference value Input current inner loop controller The modulated wave signal is obtained, which realizes the purpose of suppressing the disturbance of the load current on the output voltage and optimizing the output voltage waveform quality when the inverter is driven by a nonlinear load.

[0080] Please refer to Figure 6 , Figure 6 This is a comparison chart showing the control effects of a conventional dual-closed-loop control strategy and an inductor current reference value compensation control strategy, as provided in the embodiments of this application. Figure 6 It can be seen that the waveform quality of the output voltage when using the inductor current reference value compensation control strategy of this application to carry a nonlinear load is significantly better than that when using the conventional dual closed-loop control strategy to carry a nonlinear load, thus reducing the THD index of the output voltage.

[0081] The method for compensating the inductor current reference value provided in this application first establishes the state equation of the inverter circuit, and based on the state equation of the inverter circuit, determines the inductor current reference value compensation model containing unknown disturbances and constructs a disturbance observer to estimate the unknown disturbances; then, it acquires the output voltage reference value, the inductor current sample value, and the output voltage sample value, performs voltage outer loop control on the inverter based on the output voltage sample value and the output voltage reference value to obtain the original inductor current reference value, and inputs the inductor current sample value and the output voltage sample value into the disturbance observer to obtain the estimated value of the unknown disturbance; finally, based on the original inductor current reference value, the estimated value of the unknown disturbance, and the inductor current reference value compensation model, it obtains the compensated inductor current reference value. The method of this application estimates the disturbance amount through a disturbance observer, compensates the inductor current reference value based on the estimated disturbance amount, and uses the compensated inductor current reference value as the final inductor current reference value. This value is then fed into the current control inner loop to generate a modulation wave, thereby achieving the goal of suppressing the disturbance of the load current on the output voltage and optimizing the output voltage waveform quality when the inverter is carrying a nonlinear load.

[0082] This application also provides a non-volatile computer-readable storage medium storing computer-executable instructions that are executed by one or more processors, for example, executing the instructions described above. Figure 3 The method and steps.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in a corresponding order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method of compensating an inductor current reference value, characterized by, The method is applied to a single-phase off-grid inverter, and comprises the following steps: According to Kirchhoff's law, a state equation of an inverter circuit is established; According to the state equation of the inverter circuit, an inductance current reference value compensation model containing an unknown disturbance quantity is determined; According to the state equation of the inverter circuit, a disturbance observer for estimating the unknown disturbance quantity is constructed; An output voltage reference value, an inductance current sample value and an output voltage sample value are obtained, voltage outer loop control is performed on the inverter based on the output voltage sample value and the output voltage reference value, and an original inductance current reference value is obtained; The inductance current sample value and the output voltage sample value are input into the disturbance observer, and an estimated value of the unknown disturbance quantity is obtained; Based on the original inductance current reference value, the estimated value of the unknown disturbance quantity and the inductance current reference value compensation model, a compensated inductance current reference value is obtained; The unknown disturbance quantity is a load current, and the disturbance observer is: wherein, is an estimate of the output voltage, is an inductor current sample value, is an estimate of the unknown disturbance quantity, and is an observer coefficient, is a filter capacitance value, is an output voltage.

2. The method of claim 1, wherein, The state equation of the inverter circuit is: wherein, is a capacitance value of the filter capacitor, is an inductive current, is a capacitive current, is an output current, is an output voltage.

3. The method of claim 1, wherein, The inductance current reference value compensation model is: wherein, is the compensated inductor current reference value, is the original inductor current reference value output by the voltage outer loop controller, is the estimated value of the unknown disturbance.

4. The method of claim 1, wherein, The method for obtaining the compensated inductance current reference value based on the original inductance current reference value, the estimated value of the unknown disturbance quantity and the inductance current reference value compensation model comprises: The original inductance current reference value and the estimated value of the unknown disturbance quantity are superimposed to obtain the compensated inductance current reference value.

5. The method according to any one of claims 1 to 4, characterized in that, The method for obtaining the estimated value of the unknown disturbance quantity based on the inductance current sample value, the output voltage sample value and the disturbance observer comprises: The disturbance observer is discretized to obtain a discretized disturbance observer as follows, where Control period: The estimated value of the output voltage and the estimated value of the unknown disturbance quantity are initialized in the discretized disturbance observer; The inductance current sample value and the output voltage sample value are input into the discretized disturbance observer to obtain the estimated value of the unknown disturbance quantity in the current control period.

6. A single phase off-grid inverter characterized in that, The single-phase off-grid inverter comprises a controller, and the controller comprises at least one processor and a memory connected with the at least one processor in communication, the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the method in any one of claims 1 to 5.

7. The single-phase off-grid inverter of claim 6, wherein, The single-phase off-grid inverter further comprises a direct-current voltage input source, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a filter inductance and a filter capacitance.

8. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and when the computer program is executed by a processor, the processor executes the steps of the method in any one of claims 1 to 5.

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