A design system for a DSP-based energy feedback AC load

Abstract

This invention discloses a DSP-based energy-feeding AC load design system, relating to the field of power technology, comprising: an isolation step-down module for stepping down the input AC voltage; a load simulation module for sampling the input current and the stepped-down input voltage and sending them to the DSP control module; a DSP control module for performing A / D conversion on the sampled input current and input voltage, and outputting corresponding PWM and SPWM according to the adjustment algorithm; and a power feedback module for using a fully controlled inverter circuit based on the output PWM and SPWM, and using PI regulation to control the steady-state current and power factor, ultimately obtaining the waveform results of rectification and energy feedback.

Description

Technical Field

[0001] This invention relates to the field of power technology, specifically a DSP-based power-feed AC load design system. Background Technology

[0002] With the development of power electronics technology, high-power AC power supplies can be flexibly applied to various electrical-related fields such as power systems and motor drives. Regarding the safety performance testing, aging, lifespan, performance, and maintenance of such power supplies before they leave the factory, traditional switching loads have gradually been phased out of the market due to their poor flexibility and high cost. While existing AC load designs can flexibly change the load characteristics according to usage requirements, the high heat loss and high heat dissipation costs brought about by high voltage and high power cannot be ignored. The design of a DSP-based energy-feeding AC load not only meets the requirements of simulating flexible and varied loads such as linear resistive loads and nonlinear inductive and capacitive loads, but also uses SPWM generated by the DSP to actively invert the rectified DC-DC converter, thereby achieving energy feedback and recycling of electrical energy. This solves the energy consumption problem of traditional loads and promotes the realization of the "dual-carbon" strategic goal in industry. Furthermore, given my country's vast territory, the use of high-voltage, high-power power supplies is particularly important in both people's lives and manufacturing industries. The power system industry frequently employs various compensation methods to reduce reactive power losses. This AC load, while simulating different characteristics, can control constant current input and modify the power factor to reduce losses and compensation costs, demonstrating its excellent application prospects. Summary of the Invention

[0003] To address the shortcomings mentioned in the background section, the present invention aims to provide a DSP-based power-feed AC load design system.

[0004] The objective of this invention can be achieved through the following technical solution: a DSP-based power-feed AC load design system, comprising:

[0005] Isolation step-down module: Used to step down the input voltage of AC power;

[0006] Load simulation module: used to sample the input current and the stepped-down input voltage and send them to the DSP control module;

[0007] DSP control module: used to perform A / D conversion on the sampled input current and input voltage, and output corresponding PWM and SPWM according to the adjustment algorithm;

[0008] Power feedback module: Based on the output PWM and SPWM, it uses a fully controlled inverter circuit and PI regulation to control the steady-state current and power factor, ultimately obtaining the waveform results of rectification and energy feedback.

[0009] Optionally, the load simulation module and the power feedback module adopt an H-bridge structure, and the H-bridge circuit is composed of IRF640 with high voltage resistance.

[0010] Optionally, the process by which the load simulation module samples the input current and the stepped-down input voltage is as follows:

[0011] First, the effective value of the input AC current is obtained by sampling and calculation, thus obtaining the peak value of the input AC current. The instantaneous value V obtained by sampling is divided by the peak value to calculate the voltage phase at this time. By adding the additional phase angle Ψ corresponding to the required power factor at this time, the ideal instantaneous current value IREF under this load characteristic can be calculated. Therefore, by controlling the instantaneous current value to make it the same as the ideal current value IREF, the simulated load characteristics can be controlled.

[0012] Optionally, to control the instantaneous value of I to reach the ideal instantaneous value IEF, the actual instantaneous current value I is sampled, and a PI controller is used to regulate it. Finally, the ideal instantaneous current value IEF is obtained by turning the H-bridge on and off.

[0013] Optionally, as the AC input power gradually accumulates in the large capacitor between the analog load circuit and the energy feedback current, the voltage across the capacitor gradually increases, storing the input energy. When too much energy accumulates, the capacitor cannot hold more energy, so the power feedback module is controlled to work to perform power energy feedback.

[0014] Optionally, the power feedback module samples the voltage VDC across the large capacitor. When VDC exceeds a threshold, it generates SPWM to release the capacitor's energy.

[0015] Optionally, the PWM drive circuit uses the LKS560 half-bridge driver chip. After RC filtering, the input PWM is connected to the LKS560 chip. A bootstrap circuit is used, and a 220pF capacitor is selected to turn on the MOSFET. The MOSFET is the high-voltage IRF3710. By inputting a pair of identical PWM waves to the LKS560, the power amplifier stage switches are controlled, and a pair of complementary PWMs with load energy enhancement are output.

[0016] The beneficial effects of this invention are:

[0017] This invention utilizes the DSP's ADC sampling to generate different PWM and SPWM functions, achieving constant control of the input current, power factor adjustment, simulation of various properties, and energy feedback. During individual circuit debugging, the ADC enables precise sampling and display of AC voltage and current (including instantaneous and peak values), and DC voltage. The PWM inverter effectively achieves DC-AC conversion and feeds energy back to the grid (simulated using resistors), with an energy conversion efficiency of approximately 70%. Power factor setting and monitoring can be achieved via keyboard and screen, perfectly realizing interactive and controllable functions. The system ultimately implements a PWM rectifier and its included constant current and power control functions. Experimental results show that the designed energy-feedback AC electronic load can accurately control the discharge current of the tested power supply and feed the energy released by the tested power supply back to the grid without pollution, achieving energy regeneration and utilization. The system's stable operation and reliable performance are demonstrated. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0020] Figure 2 This is a schematic diagram of the hardware design assembly and connection according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of energy feedback across the capacitor in an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the H-bridge structure according to an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of PI control according to an embodiment of the present invention;

[0024] Figure 6 This is a schematic diagram of the Hall element used to sample the current in an embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram illustrating the DC voltage dropping to below 3.3V in an embodiment of the present invention;

[0026] Figure 8 This is a schematic diagram of the LKS560 half-bridge driver chip according to an embodiment of the present invention;

[0027] Figure 9 This is a schematic diagram of the main program logic flow of the software according to an embodiment of the present invention;

[0028] Figure 10 This is a schematic diagram of the software sampling interrupt logic control according to an embodiment of the present invention;

[0029] Figure 11 This is a schematic diagram of the current flowing through the resistor according to an embodiment of the present invention;

[0030] Figure 12 This is a waveform diagram of an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1 As shown, a DSP-based power-feed AC load design system includes:

[0033] Isolation step-down module: Used to step down the input voltage of AC power;

[0034] Load simulation module: used to sample the input current and the stepped-down input voltage and send them to the DSP control module;

[0035] DSP control module: used to perform A / D conversion on the sampled input current and input voltage, and output corresponding PWM and SPWM according to the adjustment algorithm;

[0036] Power feedback module: Based on the output PWM and SPWM, it uses a fully controlled inverter circuit and PI regulation to control the steady-state current and power factor, ultimately obtaining the waveform results of rectification and energy feedback.

[0037] In this embodiment, the system is divided into hardware design and software design, and their combination and connection method is as follows: Figure 2 , Figure 3 As shown, an H-bridge AC-DC analog resistive load circuit couples a DC-AC inverter energy feedback circuit. The H-bridge AC-DC analog electronic load modifies the phase difference between the input voltage and current, as well as the effective value of the input current, by altering the duty cycle of its left and right arms. Figure 2 If we disregard the power loss in the half-bridge, the input power will accumulate on the large capacitor, charging it and increasing the output voltage of the AC-DC circuit. When the voltage across the capacitor reaches a certain level, the DC-AC circuit will turn on, allowing energy to be fed back from the capacitor. Figure 3When the entire system is stable, the power P1 input to the energy feedback circuit is approximately equal to the power P2 consumed by the resistive load.

[0038] The hardware circuit design includes analog load, energy feedback, sampling circuit, drive circuit, control circuit, and auxiliary power supply. The sampling circuit includes input AC voltage sampling and current sampling, uses a C2000 F28069 microcontroller control board, and uses an LKS560 to drive the switching transistor to turn on and off; the auxiliary power supply includes 50V to 12V / 12V to 3.3V, etc.

[0039] The load simulation module and the power feedback module adopt an H-bridge structure. Figure 4 We selected the IRF640, which has a high voltage withstand capability, to form an H-bridge circuit.

[0040] The process by which the load simulation module samples the input current and the stepped-down input voltage is as follows:

[0041] First, the effective value of the input AC current is obtained by sampling and calculation, thus obtaining the peak value of the input AC current. The instantaneous value V obtained by sampling is divided by the peak value to calculate the voltage phase at this time. By adding the required power factor and corresponding phase angle Ψ, the ideal instantaneous current value IEF under this load characteristic is calculated. Therefore, by controlling the instantaneous current value to make it the same as the ideal current value IEF, the simulated load characteristic can be controlled. To control the instantaneous current value I to reach the ideal instantaneous current value IEF, the actual instantaneous current value I is sampled and regulated using a PI controller (e.g., ...). Figure 5 Finally, by switching the H-bridge on and off, the ideal instantaneous current value IREF is obtained. As the AC input power gradually accumulates in the large capacitor between the analog load circuit and the energy feedback current, the voltage across the capacitor gradually rises and stores the input energy. When too much energy accumulates, the capacitor cannot hold more energy, so the power feedback module is controlled to work to perform power energy feedback.

[0042] The power feedback module samples the voltage VDC across the large capacitor. When VDC exceeds a threshold, it generates SPWM to release capacitor energy. In this embodiment, for the energy feedback current, it samples the voltage VDC across the large capacitor. When VDC exceeds a certain threshold, it generates SPWM to release capacitor energy. The SPWM frequency is set to 50Hz, and the default control ratio is 1. After LC filtering to eliminate some harmonics, a relatively smooth output AC current is generated. To filter the 50Hz AC current and obtain a better filtering effect, two 2mH large inductors are used in series, and the capacitor is set to LC filtering to remove high-frequency noise, with a capacitor of approximately 3.3uF selected. The Vdc threshold is set to 50V, and then according to... To ensure that the input AC power is completely consumed by the load resistor R and that the large capacitor is not continuously charged, Pout must be greater than the maximum input power. Given an input voltage of 30V and a current of 2A, the maximum AC input power is 60W. Therefore, the load resistor R must meet the following requirements. The calculated load resistance should not exceed 20.8Ω.

[0043] In order to ensure that the harmonics of the output AC power are low, the voltage VDC across the large capacitor must be relatively stable. Therefore, it is necessary to select an electrolytic capacitor with a large capacitance for voltage stabilization and energy storage. A 4700uF large capacitor is the optimal choice.

[0044] Figure 6 For AC current sampling, a Hall element is used to sample the current, converting the 5A AC power to a 0-3.3V voltage. For DC voltage sampling, a resistor is applied to the COS8552 operational amplifier, and a voltage follower is added to the output side to reduce the DC voltage to below 3.3V (see...). Figure 7 Its reduction factor is ).

[0045] Optionally, the PWM drive circuit uses the LKS560 half-bridge driver chip. Figure 8 After RC filtering, the input PWM is connected to the LKS560 chip. Using a bootstrap circuit, a 220pF capacitor is selected to turn on the MOSFET. The MOSFET is a high-voltage IRF3710. By inputting a pair of identical PWM waves to the LKS560, the power amplifier stage switches are controlled, and a pair of complementary PWMs with load energy enhancement are output.

[0046] The overall workflow of the software system is as follows: ADC sampling; PLL obtains frequency and phase; keyboard inputs power factor, determines capacitive properties; configures duty cycle; outputs power. The main program logic flow is as follows: Figure 9 Sampling interrupt logic control such as Figure 10 .

[0047] Finally, a graded simulation test was conducted on the constructed circuit model to test the full-bridge fully controlled rectifier circuit. A 30V AC power supply was passed through an inductor and input into the full-bridge rectifier circuit. A PWM signal with a 30-degree contact angle was applied. A 1000mH inductor and a 1-ohm resistor were connected in series at the load end, and the current flowing through the resistor was observed. Figure 11 As can be seen, the steady-state voltage after full-bridge rectification is 27V. For the energy feedback circuit test, a 30V DC voltage is applied to the full-bridge circuit. The complementary SPWM generated by the DSP is connected to the corresponding bridge arm switch. An oscilloscope is placed across the load to obtain a smooth voltage waveform, as shown below. Figure 12 It can be seen that by controlling the bridge arm with SPWM and then passing it through LC, 30V DC can be inverted into smooth AC with an amplitude of 20V.

[0048] Based on the same inventive concept, this invention also provides a computer device, comprising: one or more processors, and a memory for storing one or more computer programs; the programs include program instructions, and the processor executes the program instructions stored in the memory. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, used to implement one or more instructions, specifically for loading and executing one or more instructions stored in a computer storage medium to implement the above-described method.

[0049] It should be further explained that, based on the same inventive concept, the present invention also provides a computer storage medium storing a computer program, which, when executed by a processor, performs the above-described method. This storage medium can be any combination of one or more computer-readable media. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In the present invention, the computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0050] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of this disclosure. Those skilled in the art should understand that this disclosure is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this disclosure. Various changes and modifications can be made to this disclosure without departing from its spirit and scope, and all such changes and modifications fall within the scope of this disclosure as claimed.

Claims

1. A DSP-based power-feed AC load design system, characterized in that, include: Isolation step-down module: Used to step down the input voltage of AC power; Load simulation module: used to sample the input current and the stepped-down input voltage and send them to the DSP control module; The process by which the load simulation module samples the input current and the stepped-down input voltage is as follows: First, the effective value of the input AC current is obtained by sampling and calculation, thereby obtaining the peak value of the input AC current. The instantaneous value V obtained by sampling is divided by the peak value to calculate the voltage phase φ at this time. The additional phase angle Ψ corresponding to the required power factor at this time is added to calculate the ideal instantaneous current value IREF under this load characteristic. Therefore, it is only necessary to control the instantaneous current value so that the instantaneous current value is the same as the ideal current value IREF to realize the control of the simulated load characteristics. To control the instantaneous value of I to reach the ideal instantaneous value IEF, the actual instantaneous current value I is sampled at this time, and PI is used to regulate it. Finally, the ideal instantaneous current value IEF is obtained by turning the H-bridge on and off. DSP control module: used to perform A / D conversion on the sampled input current and input voltage, and output corresponding PWM and SPWM according to the adjustment algorithm; Power feedback module: Based on the output PWM and SPWM, it uses a fully controlled inverter circuit and PI regulation to control the steady-state current and power factor, ultimately obtaining the waveform results of rectification and energy feedback.

2. The DSP-based power-feed AC load design system according to claim 1, characterized in that, The load simulation module and power feedback module adopt an H-bridge structure, and the high-voltage-resistant IRF640 is selected to form the H-bridge circuit.

3. The DSP-based power-feed AC load design system according to claim 1, characterized in that, As the AC input power gradually accumulates in the large capacitor between the analog load circuit and the energy feedback current, the voltage across the capacitor gradually increases, storing the input energy. When too much energy accumulates, the capacitor can no longer hold more energy, thus controlling the power feedback module to work and perform power energy feedback.

4. The DSP-based power-feed AC load design system according to claim 3, characterized in that, The power feedback module samples the voltage VDC across the large capacitor. When VDC exceeds the threshold, it generates SPWM to release the capacitor energy.

5. The DSP-based power-feed AC load design system according to claim 1, characterized in that, The PWM drive circuit uses the LKS560 half-bridge driver chip. After RC filtering, the input PWM is connected to the LKS560 chip. A bootstrap circuit is used, and a 220pF capacitor is selected to turn on the MOSFET. The MOSFET is the high-voltage IRF3710. By inputting a pair of identical PWM waves to the LKS560, the power amplifier stage switches are controlled, and a pair of complementary PWMs with load energy enhancement are output.

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