Inverter controller with low-voltage power supply input and control method thereof

Abstract

The invention provides a low-voltage power supply input inversion controller and a control method thereof, and relates to the technical field of power supply circuits, and the low-voltage power supply input inversion controller comprises a low-voltage power supply, a multi-level inverter and a fast terminal sliding mode controller; the low-voltage power supply, the multi-level inverter and the fast terminal sliding mode controller are sequentially connected in series; the multi-level inverter is used for converting direct current provided by the low-voltage power supply into alternating current and synthesizing an output voltage close to a sinusoidal waveform through a plurality of voltage levels; and the fast terminal sliding mode controller is used for assisting the output of the multi-level inverter to quickly reach a stable state. The rapid terminal sliding mode control is adopted to assist the output of the multi-level inverter to rapidly reach a stable state, rapid convergence of the system state can be realized in finite time, the multi-level inverter is adopted to convert the direct current provided by the low-voltage power supply into the alternating current, smoother sine waves can be generated, harmonic distortion is reduced, and the system stability is improved. The quality of output electric energy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply circuits, and in particular to an inverter controller with low voltage power input and a control method thereof. Background Art

[0002] Inverter controllers are essential components in modern power systems, especially in renewable energy power generation systems and power electronics. They not only efficiently perform DC to AC conversion, but also provide a range of additional functions, such as power quality improvement, energy management and protection, to ensure system reliability and efficiency.

[0003] The current inverter control technologies mainly include PID control and PWM technology. The PID controller measures the deviation between the output voltage and the reference voltage and adjusts the control signal according to the proportional, integral and differential components of the deviation, thereby trying to eliminate the deviation and make the output voltage track the reference voltage. PWM is a modulation technology that changes the average output voltage by adjusting the duty cycle. In the inverter, PWM is used to generate an output voltage waveform that approximates a sine wave.

[0004] However, the PID controller responds relatively slowly, especially when the system is far from the set point, and it takes a long time to converge to a stable state. Although PWM technology can generate an output voltage that is close to a sine wave, the output waveform still contains a certain amount of harmonics due to the limitation of the switching frequency. Summary of the invention

[0005] In order to solve the technical problem that the existing PID controller has a relatively slow response speed, especially when the system is far away from the set point, it takes a long time to converge to a stable state, and although the PWM technology can generate an output voltage that is approximately a sine wave, due to the limitation of the switching frequency, the output waveform still contains a certain amount of harmonics. The present invention provides an inverter controller with low voltage power input and a control method thereof.

[0006] The technical solution provided by the embodiment of the present invention is as follows:

[0007] First aspect

[0008] An inverter controller with low voltage power input provided by an embodiment of the present invention includes: a low voltage power supply, a multi-level inverter and a fast terminal sliding mode controller;

[0009] The low voltage power supply, the multilevel inverter and the fast terminal sliding mode controller are connected in series in sequence;

[0010] The multi-level inverter converts the direct current provided by the low-voltage power source into alternating current, and synthesizes an output voltage close to a sinusoidal waveform through multiple voltage levels;

[0011] The fast terminal sliding mode controller is used to assist the output of the multi-level inverter to quickly reach a stable state.

[0012] Furthermore, the low-voltage power source is specifically: a photovoltaic solar panel, a fuel cell or a battery.

[0013] Further, the low-voltage power supply includes a plurality of power supply units, and the multi-level inverter includes a plurality of single-pole single-throw switches, a plurality of diodes and a full-bridge converter;

[0014] A single power supply unit, a single single-pole single-throw switch and a single diode form a half-bridge sub-module;

[0015] A plurality of the half-bridge sub-modules are connected in series to form a half-bridge module;

[0016] The half-bridge module is connected to the full-bridge converter;

[0017] The full-bridge converter is provided with a voltage output terminal;

[0018] Among them, by controlling the on and off time of each single-pole single-throw switch, the size and polarity of the output voltage are changed, and an output voltage close to a sine waveform is synthesized.

[0019] Furthermore, in the half-bridge module, the negative pole of the power supply unit is connected to the first end of the single-pole single-throw switch, one end of the diode is connected to the positive pole of the power supply unit, and the other end is connected to the second end of the single-pole single-throw switch, so that the diode is connected in parallel between the power supply unit and the single-pole single-throw switch.

[0020] Further, the full-bridge converter includes a first switch, a second switch, a third switch and a fourth switch;

[0021] The input end of the first switch is connected to the first end of the half-bridge module, the output end of the first switch is connected to the input end of the second switch, and the input end of the second switch is connected to the second end of the half-bridge module;

[0022] The input end of the third switch is connected to the first end of the half-bridge module, the output end of the third switch is connected to the input end of the fourth switch, and the input end of the fourth switch is connected to the second end of the half-bridge module;

[0023] The voltage output terminal is provided between the output terminal of the first switch and the output terminal of the third switch;

[0024] The first switch and the fourth switch are turned on or off at the same time, and the second switch and the third switch are turned on or off at the same time, so as to change the voltage direction.

[0025] Furthermore, the multi-level inverter has an asymmetric structure, and the output voltages of the power supply units are different in magnitude.

[0026] Second aspect

[0027] A control method for an inverter controller with a low voltage power input provided by an embodiment of the present invention is applied to the inverter controller with a low voltage power input described in the first aspect, and the control method includes:

[0028] S1: constructing the sliding surface of the fast terminal sliding mode controller;

[0029] S2: determining a control voltage according to the sliding surface;

[0030] S3: Inputting the control voltage into the fast terminal sliding mode controller to assist the output of the multi-level inverter to quickly reach a stable state.

[0031] Furthermore, an objective function is constructed with the goal of minimizing the output voltage deviation value and the stabilization time required to reach convergence;

[0032] Parameters of the fast terminal sliding mode controller are optimized according to the objective function.

[0033] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0034] (1) In the present invention, fast terminal sliding mode control is used to assist the output of the multilevel inverter to quickly reach a stable state, which can achieve rapid convergence of the system state within a limited time. Even when the system is far away from the set point, it still has a good convergence effect. Even in the case of uncertainty and external interference, it can maintain good control performance.

[0035] (2) In the present invention, a multi-level inverter is used to convert the direct current provided by the low-voltage power supply into alternating current, and an output voltage close to a sine waveform is synthesized through multiple voltage levels, which can generate a smoother sine wave, thereby reducing the harmonic content, thereby greatly reducing harmonic distortion and improving the quality of output power. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0037] Figure 1 A structural block diagram of an inverter controller with low voltage power input provided by an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the structure of an inverter controller with low voltage power input provided by an embodiment of the present invention;

[0039] Figure 3 A schematic diagram of a control method for an inverter controller with a low voltage power input provided by an embodiment of the present invention.

[0040] [Reference Signs]

[0041] 1- low voltage power supply; 11- power supply unit; 2- multilevel inverter; 21- single pole single throw switch; 22- diode; 23- full bridge converter; 3- fast terminal sliding mode controller; 4- half bridge submodule. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0043] Reference Manual Attached Figure 1 , shows a structural block diagram of an inverter controller with low voltage power input provided by an embodiment of the present invention.

[0044] Reference Manual Attached Figure 2 , shows a schematic structural diagram of an inverter controller with low voltage power input provided by an embodiment of the present invention.

[0045] An embodiment of the present invention provides an inverter controller with a low-voltage power supply 1 as input, comprising: a low-voltage power supply 1 , a multi-level inverter 2 , and a fast terminal sliding mode controller 3 .

[0046] A low voltage power source 1, a multilevel inverter 2 and a fast terminal sliding mode controller 3 are connected in series in sequence.

[0047] The multilevel inverter 2 converts the direct current provided by the low-voltage power source 1 into alternating current, and synthesizes an output voltage close to a sinusoidal waveform through a plurality of voltage levels.

[0048] It should be noted that the multi-level inverter 2 is used to convert the direct current provided by the low-voltage power supply 1 into alternating current, and an output voltage close to a sine waveform is synthesized through multiple voltage levels, so that a smoother sine wave can be generated, thereby reducing the harmonic content, thereby greatly reducing harmonic distortion and improving the quality of the output power.

[0049] The fast terminal sliding mode controller 3 is used to assist the output of the multilevel inverter 2 to quickly reach a stable state.

[0050] Among them, the fast terminal sliding mode controller 3 is an improvement on the sliding mode control, which accelerates the convergence of the system state to the sliding surface by introducing special nonlinear terms, and can achieve system stability within a limited time.

[0051] It should be noted that the multi-level inverter 2 is used to convert the direct current provided by the low-voltage power supply 1 into alternating current, and an output voltage close to a sine waveform is synthesized through multiple voltage levels, so that a smoother sine wave can be generated, thereby reducing the harmonic content, thereby greatly reducing harmonic distortion and improving the quality of the output power.

[0052] Optionally, the low-voltage power source 1 is specifically: a photovoltaic solar panel, a fuel cell or a battery.

[0053] The embodiment of the present invention proposes a new multi-level inverter 2, which combines each power supply unit 11 with a single-pole single-throw switch 21 and a diode 22 into a half-bridge module, thereby improving the adaptability of the system.

[0054] In a possible implementation, the low voltage power supply 1 includes a plurality of power supply units 11, and the multilevel inverter 2 includes a plurality of single-pole single-throw switches 21, a plurality of diodes 22, and a full-bridge converter 23. A single power supply unit 11, a single single-pole single-throw switch 21, and a single diode 22 form a half-bridge submodule 4. A plurality of half-bridge submodules 4 are connected in series to form a half-bridge module. The half-bridge module is connected to the full-bridge converter 23. The full-bridge converter 23 is provided with a voltage output terminal.

[0055] It should be noted that by increasing or decreasing the number of half-bridge sub-modules 4 , the output voltage level of the system can be conveniently adjusted to adapt to different application scenarios or load requirements.

[0056] The magnitude and polarity of the output voltage are changed by controlling the on and off time of each single-pole single-throw switch 21, thereby synthesizing an output voltage close to a sine waveform.

[0057] In the present invention, the output voltage is synthesized by multiple voltage levels, which can significantly reduce the harmonic components in the output voltage. Compared with the traditional two-level inverter, the multi-level inverter 2 can generate AC power that is closer to a sine waveform, thereby improving the power quality.

[0058] Optionally, the single-pole single-throw switch 21 is specifically a MOSFET or an IGBT.

[0059] Optionally, in the half-bridge module, the negative pole of the power supply unit 11 is connected to the first end of the single-pole single-throw switch 21, one end of the diode 22 is connected to the positive pole of the power supply unit 11, and the other end is connected to the second end of the single-pole single-throw switch 21, so that the diode 22 is connected in parallel at both ends of the power supply unit 11 and the single-pole single-throw switch 21.

[0060] It should be noted that when the switch is disconnected, the current in the power supply unit 11 will stop. At this time, if there is an energy storage element (such as an inductor) in the circuit, the energy storage element will try to release the stored energy, causing the current to continue to flow through the path. The presence of the diode 22 can provide a loop for this part of the current, preventing the current from flowing in the reverse direction through the switching device, thereby protecting the switching device from damage. When the switch is disconnected, the current in the power supply unit 11 will stop. At this time, if there is an energy storage element (such as an inductor) in the circuit, the energy storage element will try to release the stored energy, causing the current to continue to flow through the path. The presence of the diode 22 can provide a loop for this part of the current, preventing the current from flowing in the reverse direction through the switching device, thereby protecting the switching device from damage. The diode 22 provides a freewheeling path, so that when the switch is disconnected, the magnetic field energy in the inductor can be released through the diode 22, avoiding excessive reverse voltage. At the same time, in the multi-level inverter 2, different power supply units 11 can generate different voltage levels through the combination of switches. By connecting the diode 22 in parallel between the power supply unit 11 and the switch, it can be ensured that during the switching process, the voltage of the power supply unit 11 is always output with the correct polarity, and the polarity of the output voltage will not be reversed due to the change of the switch state.

[0061] In the present invention, the design of connecting the diode 22 in parallel between the power supply unit 11 and the single-pole single-throw switch 21 can effectively prevent the current from flowing in reverse, ensure the correctness of the voltage polarity, simplify the control logic, and improve the reliability and efficiency of the system. This design plays a vital role in the multi-level inverter 2 and is one of the key technologies for realizing a high-performance inverter.

[0062] Optionally, the full-bridge converter 23 includes a first switch, a second switch, a third switch and a fourth switch. The input end of the first switch is connected to the first end of the half-bridge module, the output end of the first switch is connected to the input end of the second switch, and the input end of the second switch is connected to the second end of the half-bridge module. The input end of the third switch is connected to the first end of the half-bridge module, the output end of the third switch is connected to the input end of the fourth switch, and the input end of the fourth switch is connected to the second end of the half-bridge module. A voltage output end is provided between the output end of the first switch and the output end of the third switch.

[0063] The first switch and the fourth switch are turned on or off at the same time, and the second switch and the third switch are turned on or off at the same time to change the direction of the voltage. By controlling different combinations of the four switches, the magnitude and direction of the output voltage can be accurately adjusted. This enables the system to generate a smoother output voltage waveform, reduce harmonic components in the output, and improve power quality.

[0064] In the present invention, a full-bridge converter 23 including four switches is used to achieve accurate control of the output voltage, including the direction and magnitude of the voltage. This design not only improves the quality of the output voltage, but also enhances the robustness of the system, simplifies the control logic, and can achieve bidirectional power flow and four-quadrant operation.

[0065] In a possible implementation manner, the multi-level inverter 2 has an asymmetric structure, and the output voltages of the power supply units 11 are different in magnitude.

[0066] In the present invention, the asymmetric structure can synthesize the output voltage waveform more finely through different voltage levels, so that the output waveform is closer to the ideal sine waveform, thereby reducing harmonic distortion.

[0067] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0068] (1) In the present invention, fast terminal sliding mode control is used to assist the output of the multilevel inverter to quickly reach a stable state, which can achieve rapid convergence of the system state within a limited time. Even when the system is far away from the set point, it still has a good convergence effect. Even in the case of uncertainty and external interference, it can maintain good control performance.

[0069] (2) In the present invention, a multi-level inverter is used to convert the direct current provided by the low-voltage power supply into alternating current, and an output voltage close to a sine waveform is synthesized through multiple voltage levels, which can generate a smoother sine wave, thereby reducing the harmonic content, thereby greatly reducing harmonic distortion and improving the quality of the output power.

[0070] Reference Manual Attached Figure 3 , showing a flow chart of a control method of an inverter controller with low voltage power input provided by the present invention.

[0071] The present invention also provides a control method for an inverter controller with a low voltage power input, which is applied to the inverter controller with a low voltage power input, and the control method includes:

[0072] S1: Construct the sliding surface of the fast terminal sliding mode controller.

[0073] In a possible implementation manner, the recursive process of the sliding mode surface of the fast terminal sliding mode controller is specifically as follows:

[0074]

[0075] Among them, s ei represents the state variable of the i-th sliding surface, represents the derivative of the state variable of the i-th sliding surface, α i represents the linear coefficient of the i-th sliding surface, βi represents the nonlinear coefficient of the i-th sliding surface, q i 、p i represents the morphological parameters of the i-th sliding surface, q i 、p i are all positive odd numbers, and n represents the total number of sliding surfaces.

[0076] In the present invention, by introducing nonlinear terms, the design of the sliding surface can ensure that the system state converges to the sliding surface within a finite time, thereby achieving rapid response. By recursively refining the design of the sliding surface layer by layer, precise control of the system state can be achieved, ensuring that the output voltage quickly stabilizes near the expected value.

[0077] Optionally, in order to avoid the influence of singularity, the morphological parameters of the sliding surface satisfy:

[0078]

[0079] In the present invention, in the fast terminal sliding mode control, if the morphology parameters are not properly selected, the sliding surface may degenerate into a linear or quasi-linear form in some cases, thereby losing the advantage of nonlinear control. This degradation can be avoided by selecting appropriate morphology parameters to ensure the nonlinear characteristics of the sliding surface.

[0080] S2: Determine the control voltage based on the sliding surface.

[0081] In a possible implementation manner, the control voltage is specifically:

[0082] u=-sign(s e,n )

[0083] Where u represents the control voltage, si gn represents the sign function, s e,n Represents the state variable of the nth sliding surface.

[0084] It should be noted that the sign of the control voltage is determined according to the positive or negative value of the state variable of the last sliding surface, so that the system state is close to the sliding surface, helping the system state to quickly return to the sliding surface.

[0085] In the present invention, the sign of the control voltage is determined according to the positive or negative value of the state variable of the last sliding surface, which can significantly improve the dynamic response speed of the system, reduce the chattering phenomenon, and enhance the robustness and control accuracy of the system.

[0086] S3: Input a control voltage into the fast terminal sliding mode controller to assist the output of the multilevel inverter to quickly reach a stable state.

[0087] In the present invention, by constructing a sliding surface of a fast terminal sliding mode controller, determining a control voltage according to the sliding surface and inputting the control voltage into the fast terminal sliding mode controller, rapid stabilization of the output voltage of the multi-level inverter can be achieved, jittering can be reduced, and the robustness and control accuracy of the system can be enhanced.

[0088] In a possible implementation, the objective function is constructed with the goal of minimizing the output voltage deviation value and the stabilization time required to achieve convergence:

[0089] f(θ)=λT+(1-λ)E

[0090] Where f represents the objective function, θ represents the controller parameter set, T represents the stabilization time required for convergence, E represents the output voltage deviation value, and λ represents the weight coefficient of the stabilization time required for convergence.

[0091] Among them, those skilled in the art can set the size of the weight coefficient λ for achieving the stabilization time required for convergence according to actual conditions, and the present invention does not limit this.

[0092]

[0093] Among them, t i It represents the stable time required for the convergence of the i-th sliding surface.

[0094]

[0095] Among them, x(0) represents the initial state of the system.

[0096] E=|v o -v *

[0097] Where E represents the output voltage deviation value, v o Indicates the actual output voltage, v * Represents the ideal output voltage.

[0098] Parameters of the fast terminal sliding mode controller are optimized according to the objective function.

[0099] Specifically, the parameters of the fast terminal sliding mode controller can be optimized according to the objective function using a particle swarm optimization algorithm, a genetic algorithm, a simulated annealing algorithm, etc. Such optimization algorithms are already very mature prior art and will not be described in detail in the present invention.

[0100] In the present invention, by constructing an objective function and optimizing the parameters of a fast terminal sliding mode controller, the output voltage of a multi-level inverter can be quickly stabilized, the output voltage deviation value can be reduced, and the response speed and output voltage accuracy of the system can be improved.

Claims

1. An inverter controller with low voltage power input, characterized in that: include: Low voltage power supplies, multilevel inverters, and fast terminal sliding mode controllers; The low voltage power supply, the multilevel inverter and the fast terminal sliding mode controller are connected in series in sequence; The multi-level inverter converts the direct current provided by the low-voltage power source into alternating current, and synthesizes an output voltage close to a sinusoidal waveform through multiple voltage levels; The fast terminal sliding mode controller is used to assist the output of the multi-level inverter to quickly reach a stable state.

2. The inverter controller with low voltage power input according to claim 1, characterized in that: The low voltage power source is specifically: a photovoltaic solar panel, a fuel cell or a battery.

3. The inverter controller with low voltage power input according to claim 1, characterized in that: The low voltage power supply includes a plurality of power supply units, and the multi-level inverter includes a plurality of single-pole single-throw switches, a plurality of diodes and a full-bridge converter; A single power supply unit, a single single-pole single-throw switch and a single diode form a half-bridge sub-module; A plurality of the half-bridge sub-modules are connected in series to form a half-bridge module; The half-bridge module is connected to the full-bridge converter; The full-bridge converter is provided with a voltage output terminal; Among them, by controlling the on and off time of each single-pole single-throw switch, the size and polarity of the output voltage are changed, and an output voltage close to a sine waveform is synthesized.

4. The inverter controller with low voltage power input according to claim 3, characterized in that: In the half-bridge module, the negative pole of the power supply unit is connected to the first end of the single-pole single-throw switch, one end of the diode is connected to the positive pole of the power supply unit, and the other end is connected to the second end of the single-pole single-throw switch, so that the diode is connected in parallel between the power supply unit and the single-pole single-throw switch.

5. The inverter controller with low voltage power input according to claim 3, characterized in that: The full-bridge converter includes a first switch, a second switch, a third switch and a fourth switch; The input end of the first switch is connected to the first end of the half-bridge module, the output end of the first switch is connected to the input end of the second switch, and the input end of the second switch is connected to the second end of the half-bridge module; The input end of the third switch is connected to the first end of the half-bridge module, the output end of the third switch is connected to the input end of the fourth switch, and the input end of the fourth switch is connected to the second end of the half-bridge module; The voltage output terminal is provided between the output terminal of the first switch and the output terminal of the third switch; The first switch and the fourth switch are turned on or off at the same time, and the second switch and the third switch are turned on or off at the same time, so as to change the voltage direction.

6. The inverter controller with low voltage power input according to claim 3, characterized in that: The multi-level inverter has an asymmetric structure, and the output voltages of the power supply units are different in magnitude.

7. A control method for an inverter controller with low voltage power input, characterized in that: The inverter controller applied to the low voltage power input according to any one of claims 1 to 6, the control method comprising: S1: constructing the sliding surface of the fast terminal sliding mode controller; S2: determining a control voltage according to the sliding surface; S3: Inputting the control voltage into the fast terminal sliding mode controller to assist the output of the multi-level inverter to quickly reach a stable state.

8. The control method of the inverter controller with low voltage power input according to claim 7, characterized in that: The objective function is constructed with the goal of minimizing the output voltage deviation and the stabilization time required to reach convergence; Parameters of the fast terminal sliding mode controller are optimized according to the objective function.

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