An interactive boost frequency converter for a three-phase 230V power grid

Abstract

The utility model discloses an interactive boost frequency converter for three -phase 230V power grid, including box body and inside sequentially connected three -phase input EMI filter unit, three -phase rectification unit, DC boost unit, DC bus capacitor group and three -phase inverter unit, wherein, DC boost unit contains boost inductance and controllable power switch tube, and is driven by a control unit to rectify the input voltage fluctuation of wide range to the DC bus voltage of a stable boost. The utility model can keep rated power output in 200V~240V input voltage range, solves the problem that traditional passive PFC frequency converter cannot be full load under low pressure, significantly enhances its anti power grid interference ability, is applicable to the industrial application occasion of high operating stability requirement.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to an interactive boost inverter for a three-phase 230V power grid. Background Technology

[0002] In the industrial and commercial sectors, three-phase 230V frequency converters are widely used. Currently, high-power frequency converters of this power level generally employ passive power factor correction (PFC) circuits. This traditional approach has an inherent drawback: the DC bus voltage of the frequency converter directly fluctuates with the input AC grid voltage. When the grid voltage is at the lower limit of the allowable range (e.g., 200V), the DC bus voltage decreases accordingly, causing the downstream inverter circuit to be unable to synthesize sufficient voltage to drive the motor to achieve rated torque and power, thus preventing the frequency converter from operating at full load. This not only limits the full utilization of equipment performance and causes energy waste, but also forces end users to choose higher power or current-rated frequency converters to mitigate risks in unstable grid environments, significantly increasing equipment investment costs and space occupancy. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an interactive boost inverter for a three-phase 230V power grid. By introducing an innovative boost unit between rectification and inversion, it achieves active control and stabilization of the DC bus voltage, ensuring that the inverter can output full power under a wide range of input voltages.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: An interactive step-up frequency converter for a three-phase 230V power grid includes a housing and a main circuit disposed within the housing. The main circuit includes a three-phase input EMI filter unit, a three-phase rectifier unit, a DC step-up unit, a DC bus capacitor bank, a three-phase inverter unit, and a control unit.

[0005] The input terminal of the three-phase input EMI filter unit is used to connect to a 200~240V three-phase power grid, and its output terminal is connected to the AC side of the three-phase rectifier unit.

[0006] The input terminal of the DC boost unit is connected to the DC side of the three-phase rectifier unit, and it includes at least one boost inductor and at least one controllable power switch.

[0007] The input terminal of the DC bus capacitor bank is connected to the output terminal of the DC boost unit.

[0008] The DC side of the three-phase inverter unit is connected in parallel with the DC bus capacitor bank.

[0009] The control unit is configured to control the on and off of the controllable power switch. By adjusting its duty cycle, the power energy after rectification of the fluctuating input voltage is increased and stabilized at a preset DC bus voltage value, thereby keeping the output power of the frequency converter stable when the input voltage fluctuates.

[0010] Preferably, the DC boost unit includes a first boost branch and a second boost branch connected in parallel to reduce current ripple and increase power density.

[0011] Preferably, the controllable power switch is an N-channel field-effect transistor (NMOS).

[0012] Preferably, the three-phase inverter unit is a three-phase full-bridge topology, and a clamping diode is connected in series between the midpoint of each bridge arm and the DC bus to suppress turn-off overvoltage and improve system reliability.

[0013] Compared with existing technologies, the beneficial effects of the frequency converter provided by this utility model are that, by introducing an interactive boost unit, it achieves active stabilization of the DC bus voltage across the entire input voltage range, completely solving the problem that traditional frequency converters cannot operate at full load under low input voltage. This ensures that the connected motor or compressor can continuously perform at its rated performance even under conditions of grid voltage fluctuations, instantaneous drops, or imbalances. While ensuring high reliability and high performance, this utility model avoids the need for users to de-rate or over-rate equipment selection due to grid problems, effectively reducing the total system cost. Attached Figure Description

[0014] Figure 1 This is the main circuit diagram of this utility model. Detailed Implementation

[0015] The technical solution protected by this utility model will be described in detail below with reference to the accompanying drawings.

[0016] This invention proposes an interactive boost inverter for a three-phase 230V power grid, the main circuit topology of which is as follows: Figure 1As shown in the diagram. Specifically, the main circuit includes a three-phase input EMI filter unit 10, a three-phase rectifier unit 20, a DC boost unit 30, a DC bus capacitor bank 40, a three-phase inverter unit 50, and a control unit connected in sequence. The three-phase input EMI filter unit 10 is connected to a three-phase power grid with a voltage range of 200-240V. The three-phase input EMI filter unit can suppress electromagnetic interference, reduce high-frequency signal crosstalk between the power grid and the equipment, and stabilize the input voltage. The three-phase rectifier unit 20 can perform preliminary rectification from AC to DC and prevent DC current from flowing back into the power grid, thus providing a certain degree of protection for the power grid. The DC boost unit 30 rectifies and boosts the voltage of the AC power grid to the required DC voltage. The DC bus capacitor bank 40 can stabilize the DC voltage and suppress voltage fluctuations, providing a stable DC power supply for the subsequent inverter circuit. The three-phase inverter unit 50 controls the switching of IGBTs through PWM (Pulse Width Modulation) to invert the power from the DC bus into three-phase AC power.

[0017] Specifically, the three-phase input EMI filter unit is composed of components such as capacitors (C1, C2, C3, C4, C5, C6) and inductors (L2, L3, L4), used to suppress high-frequency electromagnetic interference between the power grid and the frequency converter. More specifically, the three-phase input EMI filter unit includes phase A, phase B, and phase C lines, as well as a differential-mode inductor group and a differential-mode capacitor group; wherein, The differential mode inductor group includes a first differential mode inductor La2, a second differential mode inductor La3 and a third differential mode inductor La4, which are connected in series with phase A, phase B and phase C respectively. The differential mode capacitor bank includes a first differential mode capacitor (C1, C4), a second differential mode capacitor (C2, C5), and a third differential mode capacitor (C3, C6); the two differential mode capacitor banks are respectively configured at the front and rear ends of the differential mode inductor bank. The first differential mode capacitor (C1, C4) is connected between phase A and phase B; the second differential mode capacitor (C2, C5) is connected between phase B and phase C; and the third differential mode capacitor (C3, C6) is connected between phase A and phase C.

[0018] The three-phase rectifier unit is a three-phase full-bridge rectifier circuit composed of diodes (DL1, DL2, DL3, DL4, DL9, DL10), which converts the filtered three-phase AC power into pulsating DC power.

[0019] The DC boost unit is the core of this solution. In this embodiment, an interleaved parallel boost circuit is used, including a first boost branch and a second boost branch. The first boost branch consists of a first boost inductor L4, a first boost diode DL19, and a first controllable switch S1 (NMOS transistor). The second boost branch consists of a second boost inductor L5, a second boost diode DL20, and a second controllable switch S2 (NMOS transistor). Taking the first branch as an example, one end of the first boost inductor L4 is connected to the positive output terminal of the three-phase rectifier unit, and the other end is connected to the anode of the first boost diode DL19 and the drain of the first controllable switch S1; the cathode of the first boost diode DL19 is connected to the positive terminal of the DC bus capacitor bank; the source of the first controllable switch S1 is connected to the negative terminal of the DC bus capacitor bank. The control unit sends PWM signals to the gates of the first controllable switch S1 and the second controllable switch S2 through the drive circuit to control their alternating conduction and turn-off, thereby boosting the pulsating DC current.

[0020] In this embodiment, the DC bus capacitor bank consists of four parallel 470μF electrolytic capacitors (CL9, CL10, CL11, CL12) to stabilize the boosted DC bus voltage.

[0021] The three-phase inverter unit is a three-phase full-bridge structure, consisting of six IGBTs (S10, S20, S30, S3, S40, S4) and their anti-parallel freewheeling diodes. In addition, clamping diodes (DL6, DL8, DL12, DL16, DL14, DL18) are connected in series between the midpoint of each bridge arm and the positive and negative terminals of the DC bus to absorb voltage spikes generated when the IGBTs are turned off, protecting the switching transistors.

[0022] The control unit samples the input voltage and DC bus voltage in real time, calculates the required PWM duty cycle using an algorithm, and drives the first controllable switch S1 and the second controllable switch S2 to ensure that the DC bus voltage remains stable at a preset value sufficient to support rated power output (e.g., a DC voltage higher than 340V) within the input range of 200V to 240V. This allows the inverter to continuously output a rated power of 22kW and a rated current of 50A. In this embodiment, the control unit is a DSP or MCU, and can be a high-performance MCU from STMicroelectronics (ST) such as the STM32F103 series, or a DSP from Texas Instruments (TI) such as the TMS320F2803x series.

[0023] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the description and drawings of this utility model, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. An interactive step-up frequency converter for a three-phase 230V power grid, comprising a housing and a main circuit disposed within the housing, characterized in that, The main circuit includes: The three-phase input EMI filter unit is used to connect to a 200~240V three-phase power grid. The three-phase rectifier unit has its AC side connected to the output terminal of the EMI filter unit. A DC-side boost and energy storage unit is provided, with its input terminal connected to the DC side of the three-phase rectifier unit. The DC-side boost and energy storage unit includes a DC boost module and a DC bus capacitor bank. The input terminal of the DC boost module is connected to the DC side of the three-phase rectifier unit, and it includes at least one boost inductor and one controllable power switch. The input terminal of the DC bus capacitor bank is connected to the output terminal of the DC boost unit. The three-phase inverter unit has its DC side connected in parallel with the DC bus capacitor bank; The control unit is configured to control the on and off of the controllable power switch to stabilize the DC bus voltage at a preset value.

2. The interactive step-up frequency converter for a three-phase 230V power grid according to claim 1, characterized in that, The DC boost module includes a first boost branch and a second boost branch connected in parallel. The first boost branch includes a first boost inductor, a first boost diode, and a first controllable switch. One end of the first boost inductor is connected to the DC side of the three-phase rectifier unit, and the other end is connected to the anode of the first boost diode and the anode of the first controllable switch, respectively. The cathode of the first boost diode is connected to the positive terminal of the rectifier bus capacitor bank. The cathode of the first controllable switch is connected to the negative terminal of the rectifier bus capacitor bank, and its control terminal is connected to the control unit. The second boost branch includes a second boost inductor, a second boost diode, and a second controllable switch; one end of the second boost inductor is connected to the DC side of the three-phase rectifier unit, and the other end is connected to the positive terminal of the second boost diode and the positive terminal of the second controllable switch, respectively; the negative terminal of the second boost diode is connected to the positive terminal of the rectifier bus capacitor bank; the negative terminal of the second controllable switch is connected to the negative terminal of the rectifier bus capacitor bank, and its control terminal is connected to the control unit.

3. An interactive step-up frequency converter for a three-phase 230V power grid according to claim 2, characterized in that, The first controllable switch and the second controllable switch are NMOS transistors, with the drain of the first controllable switch and the source of the second controllable switch serving as their respective positive terminals, the gate of the first controllable switch and the gate of the second controllable switch serving as their respective control terminals.

4. An interactive step-up frequency converter for a three-phase 230V power grid according to claim 1, characterized in that, The DC bus capacitor bank consists of four electrolytic capacitors with a capacity of 470μF connected in parallel.

5. An interactive step-up frequency converter for a three-phase 230V power grid according to claim 1, characterized in that, The three-phase input EMI filter unit includes an A-phase line, a B-phase line, and a C-phase line, as well as a differential-mode inductor group and a differential-mode capacitor group; The differential mode inductor group includes a first differential mode inductor, a second differential mode inductor and a third differential mode inductor, which are connected in series with phase A, phase B and phase C respectively; The differential mode capacitor bank includes a first differential mode capacitor, a second differential mode capacitor, and a third differential mode capacitor; the first differential mode capacitor is connected between phase A and phase B; the second differential mode capacitor is connected between phase B and phase C; and the third differential mode capacitor is connected between phase A and phase C.

6. An interactive step-up frequency converter for a three-phase 230V power grid according to claim 1, characterized in that, The three-phase rectifier unit is a six-channel rectifier bridge.

7. An interactive step-up frequency converter for a three-phase 230V power grid according to claim 1, characterized in that, The three-phase inverter unit is a three-phase full-bridge structure, and a clamping diode for overvoltage clamping is connected in series between the midpoint of each bridge arm and the DC bus.

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