RU119546U1 - THREE-PHASE VOLTAGE CONVERTER - Google Patents

Abstract

A three-phase AC-to-DC converter containing current sensors in the phases of the supply network, a three-phase choke on the AC side connected to the inputs of a three-phase bridge inverter made on IGBT transistors with antiparallel diodes, a smoothing capacitor with a voltage sensor is connected to the output of the inverter and microcontroller, characterized in that the microcontroller implements a slave control system that implements a sliding current control mode and maintains the output voltage at the same level.

Description

The utility model relates to power supply systems, in particular to electric energy conversion devices, and can be used to obtain a stabilized DC voltage of the required value from a three-phase voltage of 380 V and to provide a two-way energy exchange between AC and DC circuits or as a secondary power source of a variable AC drive current.

Known stabilizing converter of an alternating three-phase voltage to constant (RF patent for utility model No. 63134). The stabilizing converter contains a series-connected radio-frequency filter, an input rectifier, an input and capacitance filter measuring and protection unit, a high-frequency transistor inverter, a high-frequency step-down transformer, an output rectifier, an LC filter and an output measuring and protection unit. There is also a control unit, the inputs of which are connected to the potential measurement output of the output measurement and protection unit and the current and potential measurement outputs of the output measurement and protection unit, and the outputs are connected to the inverter control inputs and the switching inputs of the output measurement and protection unit.

A disadvantage of the known solution is the impossibility of consuming a sinusoidal current from the supply network and the inability to establish the input current in phase with the supply voltage.

A known three-phase AC voltage converter (RF patent for utility model No. 106465), comprising a transformer with primary and secondary windings located on a single-phase magnetic circuit, the primary winding of which is connected to a four-wire three-phase network through a valve bridge and controllable valve elements, and the secondary winding is connected to load. The primary winding of the transformer with one clamp is connected directly to the output of the valve bridge, and the other with a neutral wire. The valve bridge is made on fully controllable elements, the output of which is shorted.

The disadvantage of this converter is its complex design and significant weight and size characteristics.

The proposed converter of alternating three-phase voltage to DC allows you to change the level of the output voltage both above and below the amplitude of the first harmonic of the input voltage, in addition to ensure:

- two-way energy connection between AC and DC circuits;

- the sinusoidal shape of the current consumed from the network;

- compensation of reactive power of other power consumers in the network.

The described advantages are achieved in that the three-phase AC to DC converter contains a microcontroller that controls the on and off of IGBT transistors. By changing the duty cycle of the control signals, it is possible to regulate the value of the output voltage of the controller both above and below the input voltage value and control the energy of the input choke. The higher the frequency of the control signals, the lower the value of the capacitance of the smoothing capacitor. The inductance value of a three-phase inductor is practically independent of the switching frequency, but is determined by the power consumed in the load.

Figure 1 presents the General functional diagram of the proposed Converter three-phase voltage to DC.

The AC three-phase to DC voltage converter contains current sensors 1 in the phases of the supply network, a three-phase inductor 2, a three-phase bridge inverter 3, made on IGBT transistors with counter-parallel diodes, a smoothing capacitor 4, a voltage sensor 5 on the capacitor, a microcontroller 6 with analog a digital converter comprising an adder 7, a voltage regulator 8, a coordinate transformer 9, an adder 10 and a current regulator 11, and a control system of 12 GW transistors.

The operation of the circuit is as follows. The alternating voltage of a three-phase network 380 V through current sensors 1 in phases A, B and C and a three-phase inductor 2 is fed to the input of a three-phase bridge inverter 3. The output voltage is supplied to a smoothing capacitor 4 selected from operating conditions at a high constant voltage of up to 1000 V. the output voltage is measured by the voltage sensor 5. The measured value of the output voltage is supplied to the microcontroller 6 at the input of the adder 7. The current voltage value is subtracted from the set value and fed to the input of the voltage regulator 8. In The voltage regulator generates a set value of the active current consumed from the network (i _act ), which is fed to the input of the coordinate transformer 9. The coordinate converter generates from the set values of the active and reactive (i _react ) currents in the rotating coordinate system the current values in phases i _A , i _B and i _C in a fixed coordinate system, which are fed to the input of adder 10. In adder 10, current values in phases are subtracted from the current values in phases, and the resulting differences are fed to the input of current regulator 11. In current regulator 11 commands are formed for the control system of 12 GW transistors. The control system 12 generates pulses on and off IGBT transistors. To ensure a sufficiently high efficiency, the direct voltage drop across IGBT transistors and diodes does not exceed 0.5-1.5 V, and the on and off time of the transistors is no more than 0.5-1 μs, which allows operating at frequencies up to 100 kHz.

The dual-circuit slave control system organized in the microcontroller, which, to stabilize the output voltage and ensure two-way energy exchange between AC and DC circuits, maintains the voltage at the smoothing capacitor 4 at the same level. The current loop is internal to the voltage stabilization loop. Current feedback is implemented in a fixed coordinate system, and the current controller is relay-controlled, providing a sliding current control “current corridor”. Using the current corridor allows you to automatically generate pulse-width control of IGBT transistors of a three-phase bridge inverter 3. The microcontroller receives information about the parameters of the generated and consumed electric energy - the instantaneous values of the generated voltage and the current consumed from the mains in phases, the duration of the on-time is calculated from the measured and set parameters and off state of IGBTs of a three-phase bridge inverter.

Thus, the proposed embodiment of the circuitry for the implementation of an electric converter of an alternating three-phase voltage into a constant voltage makes it possible to obtain an adjustable output voltage level from zero to a voltage higher than the input voltage level, to provide a two-way energy exchange between direct and alternating current circuits, a sinusoidal shape of the current consumed from the network, and to compensate for the reactive power of other power consumers in the network.

Claims (1)

A three-phase AC to DC converter containing current sensors in the phases of the supply network, a three-phase inductor on the AC side, connected to the inputs of a three-phase bridge inverter made on IGBT transistors with counter-parallel diodes, a smoothing capacitor with a voltage sensor and connected to the inverter output microcontroller, characterized in that the microcontroller implements a slave control system that implements a sliding current control mode and supports one level output voltage.