Inverter for improving loading capacity of low-PF load

Abstract

The utility model provides an inverter capable of improving the loading capacity of a low-PF load. The system comprises a battery pack, a DC input filter circuit, an isolation DC-DC circuit, a high-voltage DC bus filter circuit, a DC-AC inverter bridge circuit, an AC LC filter circuit, a DC voltage and current isolation sampling circuit, a DC-DC isolation driving circuit, a bus voltage and current sampling circuit, a DC-AC isolation driving circuit, a load voltage and current sampling circuit, an AC output port and a DSP main control chip. A human-computer interface and a DC auxiliary power supply circuit are displayed and arranged; by adopting a two-stage voltage platform, when the current reaches a preset value, a DSP main control chip can control the duty ratio of a DC-AC inverter bridge circuit, so that the output voltage can be gradually reduced to 80% of the rated output voltage; when the voltage is reduced to 80% of the rated output voltage, the current loop is released, and the output power can be increased; when the output power reaches 1.2 times of the rated power, the output current is 1.5 times of the rated current, and the purpose that overload protection is not prone to happening to the load with the low PF value is achieved.

Description

Technical Field

[0001] This utility model relates to the field of inverter technology, and more particularly to an inverter that improves the load-carrying capacity of low power factor (PF) loads. Background Technology

[0002] Currently, most inverters on the market use constant current mode or constant power mode to improve load capacity. However, when driving low-PF loads with low voltage protection, the output voltage drops quickly to the low-voltage protection threshold under constant current mode, causing the load to malfunction and prevent normal operation. Under constant power mode, the inverter's output voltage fluctuates due to changes in the load's operating power, and the load also malfunctions, such as with welding machines, and may even damage the load. Utility Model Content

[0003] The problem to be solved by this utility model is to provide an inverter that improves the load-carrying capacity of low PF loads, so as to achieve the purpose of preventing overload protection when carrying low PF loads.

[0004] To solve the above technical problems, an inverter with improved low-PF load carrying capacity is provided by this utility model, comprising a battery pack, a DC input filter circuit, an isolated DC-DC circuit, a high-voltage DC bus filter circuit, a DC-AC inverter bridge circuit, an AC LC filter circuit, a DC voltage and current isolated sampling circuit, a DC-DC isolated drive circuit, a bus voltage and current sampling circuit, a DC-AC isolated drive circuit, a load voltage and current sampling circuit, an AC output port, a DSP main control chip, a display and setting human-machine interface, and a DC auxiliary power supply circuit;

[0005] The display and settings human-machine interface allows you to set the rated output current of the inverter, and the DSP main control chip can perform subsequent calculations and control based on the set rated current;

[0006] The load voltage and current sampling circuit allows the DSP main control chip to read the load current and voltage in real time;

[0007] When the current value read by the DSP main control chip is less than the set rated current, the DSP main control chip controls the output voltage to the rated output voltage through the voltage loop.

[0008] When the DSP main control chip reads that the load current reaches 1.2 times the rated current, the DSP main control chip switches to the voltage loop and current loop simultaneously to control the duty cycle of the switching transistor of the DC-AC inverter bridge circuit, so that the output current is kept constant at 1.2 times the rated current and the output voltage is lower than the rated output voltage.

[0009] When the output voltage drops to 80% of the rated voltage, the DSP main control chip controls the output voltage to stabilize at 80% of the rated voltage through the voltage loop, and the DSP main control chip changes the value of the current loop to 150% of the rated current.

[0010] When the load current is greater than 120% of the rated current but less than 150% of the rated current, the output voltage will be maintained at 80% of the rated output voltage.

[0011] When the load current exceeds 150% of the rated current, the inverter will enter a protection state and shut down the drive of the DC-AC inverter bridge circuit.

[0012] When the load current is less than 120% of the rated current, the output voltage returns to the rated output voltage.

[0013] The beneficial effects of this invention are as follows: This invention provides an inverter that improves the load-carrying capacity of low power factor (PF) loads. By employing a two-stage voltage platform, when the current reaches a preset value, the DSP main control chip controls the duty cycle of the DC-AC inverter bridge circuit, causing the output voltage to gradually decrease to 80% of the rated output voltage. After the voltage drops to 80% of the rated output voltage, the current loop is released, allowing the output power to increase. When the output power reaches 1.2 times the rated power, overload protection is activated. The advantage of this is that after voltage reduction, when the power reaches 1.2 times, the output current is 1.5 times the rated current, achieving the goal of preventing overload protection when driving low power factor loads. Attached Figure Description

[0014] Figure 1 The working module block diagram of the inverter of this utility model is shown.

[0015] Figure 2 The circuit diagrams of the bus voltage sampling circuit, DSP main control chip, load voltage and current sampling circuit, and DC-AC isolation drive circuit of this utility model are illustrated.

[0016] Figure 3 The circuit diagrams of the isolated DC-DC circuit, high-voltage DC bus filter circuit, DC-AC inverter bridge circuit, and DC auxiliary power supply circuit of this utility model are illustrated.

[0017] Figure 4 The circuit diagram of the human-machine interface display settings of this utility model is illustrated. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure.

[0019] Based on the embodiments described in this disclosure, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this disclosure.

[0020] refer to Figure 1-4 .

[0021] This utility model provides an inverter that improves the load-carrying capacity of low PF loads, comprising a battery pack, a DC input filter circuit, an isolated DC-DC circuit, a high-voltage DC bus filter circuit, a DC-AC inverter bridge circuit, an AC LC filter circuit, a DC voltage and current isolated sampling circuit, a DC-DC isolated drive circuit, a bus voltage and current sampling circuit, a DC-AC isolated drive circuit, a load voltage and current sampling circuit, an AC output port, a DSP main control chip, a display and setting human-machine interface, and a DC auxiliary power supply circuit;

[0022] The display and settings human-machine interface allows you to set the rated output current of the inverter, and the DSP main control chip can perform subsequent calculations and control based on the set rated current;

[0023] The load voltage and current sampling circuit allows the DSP main control chip to read the load current and voltage in real time;

[0024] When the current value read by the DSP main control chip is less than the set rated current, the DSP main control chip controls the output voltage to the rated output voltage through the voltage loop.

[0025] When the DSP main control chip reads that the load current reaches 1.2 times the rated current, the DSP main control chip switches to the voltage loop and current loop simultaneously to control the duty cycle of the switching transistor of the DC-AC inverter bridge circuit, so that the output current is kept constant at 1.2 times the rated current and the output voltage is lower than the rated output voltage.

[0026] When the output voltage drops to 80% of the rated voltage, the DSP main control chip controls the output voltage to stabilize at 80% of the rated voltage through the voltage loop, and the DSP main control chip changes the value of the current loop to 150% of the rated current.

[0027] When the load current is greater than 120% of the rated current but less than 150% of the rated current, the output voltage will be maintained at 80% of the rated output voltage.

[0028] When the load current exceeds 150% of the rated current, the inverter will enter a protection state and shut down the drive of the DC-AC inverter bridge circuit.

[0029] When the load current is less than 120% of the rated current, the output voltage returns to the rated output voltage.

[0030] It employs a two-stage control method: first, a voltage loop stabilizes the output voltage at the rated voltage; then, when the load current reaches 1.2 times the rated current, a current loop stabilizes the output current at a constant 1.2 times the rated current, while the DSP main control chip adjusts the target voltage to 80% of the rated voltage; when the output voltage drops to 80% of the rated voltage, the current is released; and overload protection only occurs when the load power reaches 120% of the rated power. This alteration of the two voltage platforms is particularly effective for loads with low power factor (PF). In contrast, a load that requires 6kW to operate using constant current or constant power mode can be driven by only 3500W using this two-stage loop control method. By employing a two-stage voltage platform, when the current reaches a preset value, the DSP main control chip controls the duty cycle of the DC-AC inverter bridge circuit, causing the output voltage to gradually decrease to 80% of the rated output voltage. The 80% threshold ensures the voltage doesn't drop too low, as this could trigger undervoltage protection on some loads, preventing them from operating. Once the voltage reaches 80% of the rated output voltage, the current loop is released to allow the output power to increase. When the output power reaches 1.2 times the rated power, overload protection is activated. The advantage of this is that after voltage reduction, when the power reaches 1.2 times the rated power, the output current is 1.5 times the rated current, thus reducing the likelihood of overload protection when driving low-pF loads.

[0031] The above embodiments are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. An inverter that improves the load-carrying capacity of low power factor (PF) loads, characterized in that, It includes a battery pack, DC input filter circuit, isolated DC-DC circuit, high voltage DC bus filter circuit, DC-AC inverter bridge circuit, AC LC filter circuit, DC voltage and current isolated sampling circuit, DC-DC isolated drive circuit, bus voltage and current sampling circuit, DC-AC isolated drive circuit, load voltage and current sampling circuit, AC output port, DSP main control chip, display and setting human-machine interface, and DC auxiliary power supply circuit. The display and setting human-machine interface can set the rated output current of the inverter, and the DSP main control chip can perform subsequent calculations and control according to the set rated current; The load voltage and current sampling circuit enables the DSP main control chip to read the load current and voltage in real time; When the current value read by the DSP main control chip is less than the set rated current, the DSP main control chip controls the output voltage to the rated output voltage through the voltage loop; When the DSP main control chip reads that the load current reaches 1.2 times the rated current, the DSP main control chip switches to the voltage loop and current loop simultaneously to control the duty cycle of the switching transistor of the DC-AC inverter bridge circuit, so that the output current is kept constant at 1.2 times the rated current and the output voltage is lower than the rated output voltage. When the output voltage drops to 80% of the rated voltage, the DSP main control chip controls the output voltage to stabilize at 80% of the rated voltage through the voltage loop, and the DSP main control chip changes the value of the current loop to 150% of the rated current. When the load current is greater than 120% of the rated current but less than 150% of the rated current, the output voltage will be maintained at 80% of the rated output voltage. When the load current exceeds 150% of the rated current, the inverter will enter a protection state and shut down the drive of the DC-AC inverter bridge circuit. When the load current is less than 120% of the rated current, the output voltage returns to the rated output voltage.

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