Key Technology Research Of Direct-expansion Solar Assisted Heat Pump's Adjustment And Control

Direct-expansion solar assisted heat pump system is to combine organically solar heat utilization technology with the conventional air source heat pump to furthest absorb solar heat outside low quality heat, which is a new type of green equipment with the combination of heat pump air-condition and heat pump water heater. These years, 'energy-saving, environmental protection protection, reducing consumption' have been pay more attention to our country and have been supported by the Tenth Fine-Year Plan and 11th Five-Year Plan. So the development of direct-expansion solar assisted heat pump system has prominent economic and society benefit.As solar collector and outside evaporator are fixed in parallel in direct-expansion solar assisted heat pump system, the system thermodynamic cycle air-conditioning system to pursue the best operating conditions quality is the first consideration of control strategy. On the other hand, water tank is designed to maximum store heat energy in the system, so as to make up the lack of light time and shortage of long time low-grade heat source. Due to the change of system structure and control objective, obviously conventional heat pump control strategy and method can not be copied. Compared with conventional heat pump system, direct-expansion solar assisted heat pump system has common character and its peculiarities. The sdudy of control strategy and method in direct-expansion solar assisted heat pump is the key that this technology goes to perfect. This is hot topic of solar thermal use area in recent years the, the technology is the focus of research in the field.Advanced heat pump technology lab of Shandong University of Science and Technology exploited a suit of minitype direct-expansion solar assisted heat pump multi-function machine in November 2005. In the succedent two years, the subject group have done a lot of work and gained new research progress. This topic researches compressor's variable frequency technology, EEV's control technology and working performance of direct-expansion solar assisted heat pump. In order to realize optimum working character, VFC is adopted to realize dynamic matching between variable-frequency compressor's rotate speed and room heat loading; EEV is adopted to realize realize dynamic matching between refrigeration flux and evaporator load.This paper researches compressor's variable-frequency system and EEV's throttle system used theory analyse and system simulation, sets up VFC and EEV's mathematical model used steady-state centralized parametric method, proposes VFC and EEV's PID control tactic and simulation arithmetic. Aimed at setting of PID control parameters, this paper simulates closed-loop time-domain characteristic of VFC and EEV's control system. We confirm K_p, T_i, T_d of PID adjustor using time-domain characteristic analyse. Simulation results show that system's control characteristic improves prominently adopting PID control.Basing on credible and accurate thermal parameters, aiming at room heat loading and evaporator's superheat degree, this paper brings forward control project which used PLC as microprocessor, touched screen as real-time monitor. It introduces VFC-EEV experimental system's control principle and presents software and hardware design of VFC-EEV control system.This subject research gets hold of the science and technology plan item of Qingdao, 2007. Item number is 07-2-2-22-jch.