Abstract

Provided is a power conversion system. The system comprises: a rectifier module, which converts an alternating-current input voltage into a direct-current bus voltage; an inverter module, which converts the direct-current bus voltage into an alternating-current output voltage; and a control module, which generates control signals for the rectifier module and the inverter module, wherein the switching frequency of a power switch tube in the rectifier module is an even multiple of the switching frequency of a power switch tube in the inverter module, and end points of a PWM carrier of the power switch tube in the inverter module are respectively aligned with end points of a PWM carrier of the power switch tube in the rectifier module. In the present invention, by using a topological structure of a rectifier at the front stage and an inverter at the rear stage, high-frequency ripple currents at two ends of a direct-current bus energy storage capacitor can be greatly reduced, and losses of the energy storage capacitor can be reduced, such that the capacity, size and cost of the direct-current bus energy storage capacitor can be greatly reduced, thereby improving the power density and reliability of a system.

IPC Classes  ?

• H02M 5/44 - Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC by static converters using discharge tubes or semiconductor devices to convert the intermediate DC into AC
• H02M 5/458 - Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC by static converters using discharge tubes or semiconductor devices to convert the intermediate DC into AC using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
• H02P 27/08 - Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using DC to AC converters or inverters with pulse width modulation
• H02P 25/024 - Synchronous motors controlled by supply frequency

Abstract

Provided are a compressor variable-frequency speed regulation system and a direct-current bus voltage overvoltage protection method, comprising: during the process of motor speed regulation, setting a direct-current bus voltage given value on the basis of the motor rotational speed, and controlling a direct-current bus voltage actual value to track the direct-current bus voltage given value; setting a direct-current bus voltage limiting point to follow the direct-current bus voltage given value and be larger than the direct-current bus voltage given value, and setting a direct-current bus voltage limiting recovery point to follow the direct-current bus voltage given value and be smaller than the direct-current bus voltage given value; when the direct-current bus voltage actual value is larger than or equal to the direct-current bus voltage limiting point, controlling a power switch to stop operating until the direct-current bus voltage actual value is smaller than or equal to the direct-current bus voltage limiting recovery point, and controlling the power switch to resume operating. The present invention increases system efficiency, reduces the risk of direct current bus energy storage capacitor and power switch faults, decreases rectification module and inversion module loss during light loads, and prevents mistaken power switch turn-off.

IPC Classes  ?

• H02P 29/024 - Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
• H02P 29/032 - Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
• H02P 27/06 - Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using DC to AC converters or inverters
• H02P 25/024 - Synchronous motors controlled by supply frequency
• H02H 7/09 - Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against over-voltageEmergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against reduction of voltageEmergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against phase interruption

Abstract

A compressor variable-frequency speed adjusting system and a control method for a direct-current bus voltage, comprising: a rectifier module, for converting an alternating-current input voltage into a direct-current bus voltage; an inverter module, for converting the direct-current bus voltage into an electric motor driving voltage; an electric motor, driven by the electric motor driving voltage to operate; and a control module, used for adjusting the direct-current bus voltage outputted by the rectifier module. When the electric motor is operating below a rated rotational speed, the direct-current bus voltage is outputted on the basis of the alternating-current input voltage; and, when the electric motor is operating over the rated rotational speed, the direct-current bus voltage is outputted on the basis of the alternating-current input voltage and of the rotational speed of the electric motor. The control method greatly reduces low-order harmonics of an electrical grid, increases system efficiency, and puts the variable-frequency speed adjusting system in the most efficient work mode.

IPC Classes  ?

• H02M 5/44 - Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC by static converters using discharge tubes or semiconductor devices to convert the intermediate DC into AC
• H02P 27/06 - Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using DC to AC converters or inverters
• H02P 25/024 - Synchronous motors controlled by supply frequency
• H02J 3/01 - Arrangements for reducing harmonics or ripples