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1. A multi-outdoor unit parallel type non-reversing defrosting system, comprising an indoor heat exchanger (1) and three or more outdoor units (2) arranged in parallel, wherein the outdoor units (2) each comprise a compressor (21), a four-way valve (22), an outdoor heat exchanger (23), a first solenoid valve (24), and a bypass branch; four interfaces of the four-way valve (22) are connected to a discharge end of the compressor (21), a refrigerant return end of the compressor (21), the first solenoid valve (24), and the outdoor heat exchanger (23), respectively; the first solenoid valves (24) of the outdoor units (2) are converged and connected to one end of the indoor heat exchanger (1), and the outdoor heat exchangers (23) of the outdoor units (2) are converged and connected to the other end of the indoor heat exchanger (1); both ends of the bypass branch are respectively in bypass connection to a pipeline between the four-way valve (22) and the outdoor heat exchanger (23) and a pipeline between the first solenoid valve (24) and the indoor heat exchanger (1); the bypass branch is provided with a second solenoid valve (25) configured to control connection and disconnection of the bypass branch; when it is monitored that any outdoor unit (2) is abnormal in frosting, the outdoor units (2) which are not frosted are operated as required on the basis of a current heating energy requirement A of the indoor heat exchanger (1), and after the started outdoor units (2) run to a target frequency, the outdoor units (2) are operated as required on the basis of the heating energy requirement A and a defrosting energy requirement B of the frosted outdoor unit (2), and meanwhile, the bypass branch of the frosted outdoor unit (2) is controlled to be connected till it is monitored that defrosting is completed.
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