Patent Publication Number: US-2016231010-A1

Title: Photovoltaic air conditioning system

Description:
TECHNICAL FIELD OF THE DISCLOSURE 
     The disclosure relates to the technical field of power electronics and air conditioning cooling, and in particular to a photovoltaic air conditioning system. 
     BACKGROUND OF THE DISCLOSURE 
     Solar energy, as clean energy, attracts more and more attention of people, and along with development of an electrical energy and an air conditioning technology, technologies of employing photovoltaic energy as energy for air conditioners emerge, and related technologies have been disclosed in many patents and dissertations. For example, Chinese disclosure patent application CN102705944A discloses a solar variable frequency air conditioning system, which includes an inverter module and an air conditioning frequency converter of a rectifier and inverter grid connection module, implements supplying of power to an air conditioner through a photovoltaic cell and also implements grid-connected power generation. 
     However, a photovoltaic air conditioning system in a conventional art has the problem of poor applicability, and there are more limits to auxiliary facilities. This is because a grid connection inverter module required by grid connection is a part of a frequency converter of an air conditioning unit in the conventional art and then the air conditioning unit is required to be powered on during grid-connected power generation, which may cause energy waste and influence on service life of the air conditioning unit. Moreover, only a photovoltaic cell component equivalent to power of the air conditioning unit may be configured under the limit of capacity of the air conditioning frequency converter, so that only a new photovoltaic power generation system may be established to be matched with the air conditioning system, and the air conditioning system may not be connected to an existing photovoltaic power plant, otherwise it is impossible to connect all electric energy generated by the photovoltaic power plant to a grid under the limit of capacity of the air conditioning frequency converter, which may cause great waste of the electric energy. 
     In addition, the conventional art also has the problem that an electronic power device such as an inverter and a current converter in a photovoltaic power generation system during shutdown of an air conditioning unit. 
     SUMMARY OF THE DISCLOSURE 
     In order to overcome shortcomings of the conventional art, the embodiment of the disclosure provides a photovoltaic air conditioning system, to solve the problem of poor applicability of a photovoltaic air conditioning system in the conventional art. 
     The embodiment of the disclosure provides the following technical solutions. 
     A photovoltaic air conditioning system is provided, which includes a photovoltaic cell array, an air conditioning unit, a current conversion unit, a first direct current bus-bar and a second direct current bus-bar, wherein the air conditioning unit further includes a first inverter module configured to supply power to the air conditioning unit and serving as a standard accessory of the air conditioning unit, and capacity of the first inverter module is configured according to power of the air conditioning unit; the current conversion unit is an independent structure, first end of the current conversion unit is connected with a public grid, second end of the current conversion unit is electrically connected with the first inverter module through the first direct current bus-bar, and capacity of the current conversion unit is configured according to a requirement of the photovoltaic cell array and/or the public grid; and the photovoltaic cell array is electrically connected with the first direct current bus-bar through the second direct current bus-bar. 
     Preferably, when output power of the photovoltaic cell array is higher than or equal to input power required by running of the air conditioning unit, the air conditioning unit is powered by the photovoltaic cell array only; and 
     when the output power of the photovoltaic cell array is lower than the input power required by running of the air conditioning unit, the air conditioning unit is jointly powered by the public grid and the photovoltaic cell array. 
     Preferably, when the output power of the photovoltaic cell array is higher than the input power required by running of the air conditioning unit, or when the air conditioning unit does not work, the current conversion unit is configured to convert direct current output by the photovoltaic cell array into alternating current for transmission to the public grid. 
     Preferably, the current conversion unit includes a rectifier module and a second inverter module. 
     Preferably, the current conversion unit is a four-quadrant current converter. 
     Preferably, the photovoltaic air conditioning system further includes a photovoltaic collector unit and power distribution unit which are arranged between the photovoltaic cell array and the second direct current bus-bar, and the photovoltaic cell array, the photovoltaic collector unit, the power allocation unit and the second direct current bus-bar are sequentially connected. 
     Preferably, the air conditioning unit is a centrifugal water-cooled air conditioning unit or a screw type water-cooled air conditioning unit. 
     Preferably, the photovoltaic air conditioning system further includes a current conversion unit cooling device. 
     Preferably, the air conditioning unit further includes an evaporator and a first condenser, the current conversion unit cooling device includes a coolant pump, throttling element and heat exchanger which are sequentially connected in series, a first end of the coolant pump is communicated with the first condenser, a second end is communicated with the throttling element, a first end of the heat exchanger is communicated with the throttling element, a second end is communicated with the evaporator, and the current conversion unit is cooled by heat exchange of the heat exchanger and the current conversion unit. 
     Preferably, the current conversion unit cooling device further includes a one-way valve, the one-way valve is connected in parallel with the coolant pump, an inlet of the one-way valve is communicated with the first condenser, and an outlet is communicated with the throttling element. 
     Preferably, the air conditioning system further includes a second condenser, and the second condenser is connected between the heat exchanger and the evaporator. 
     The embodiment of the disclosure has the beneficial effects that: the photovoltaic air conditioning system provided by the embodiment of the disclosure may be adapted to various photovoltaic power plants with different capacities, and a photovoltaic power plant may be seamlessly and effectively combined with a heat ventilation air conditioner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structure diagram of a photovoltaic air conditioning system according to embodiment 1 of the disclosure; and 
         FIG. 2  is a diagram of a frequency conversion unit cooling structure of a photovoltaic air conditioning system according to embodiment 2 of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In order to make a purpose, technical solutions and advantages of the disclosure clearer, the disclosure will be further described below with reference to the drawings and embodiments in detail. It should be understood that specific embodiments described here are only adopted to explain the disclosure and not intended to limit the disclosure. 
     Embodiment 1 
       FIG. 1  is a structure diagram of a photovoltaic air conditioning system according to embodiment 1 of the disclosure, and the photovoltaic air conditioning system includes a photovoltaic cell array  10 , a current conversion unit  20 , an air conditioning unit  30 , a first direct current bus-bar  40  and a second direct current bus-bar  50 . The air conditioning unit  30  further includes a first inverter module  31 , the first inverter module  31 , as a part of an air conditioning frequency converter, belongs to a standard accessory of the air conditioning unit  30 , the first inverter module  31  is configured to current direct current into alternating current for supply to a load  32 , the load  32  at least includes a variable frequency compressor of the air conditioning unit, and capacity of the first inverter module  31  is configured according to a power requirement of the air conditioning unit  30 . Preferably, the first inverter module  31  is arranged onboard, and is mounted on the air conditioning unit  30 . 
     The photovoltaic cell array  10  is connected with the first direct current bus-bar  40  through the second direct current bus-bar  50 , so that the direct current generated by the photovoltaic cell array  10  is directly supplied to the air conditioning unit  30  through the second direct current bus-bar  50  and the first direct current bus-bar  40 . 
     The current conversion unit  20  is an independent structure, its one end is connected with a public grid  60 , and the other end is connected with the first inverter module  31  through the first direct current bus-bar  40 . The current conversion unit  20  includes a rectifier module and a second inverter module, the rectifier module  21  is configured to convert alternating current of the public grid  60  into direct current for supply to the air conditioning unit  30 , and the second inverter module is configured for photovoltaic grid-connection power generation, and is configured to convert the direct current generated by the photovoltaic cell array  10  into alternating current for connection to the public grid  60 . Capacity of the current conversion unit  20  is configured according to a requirement of the photovoltaic cell array  10  and/or the public grid  60 . The current conversion unit  20 , as an independent structure, may not be limited by the air conditioning unit, and may also be conveniently wired and mounted according to a construction requirement of a photovoltaic power plant. A first main function of the current conversion unit  20  is to implement Maximum Power Point Tracking (MPPT) of the photovoltaic cell array  10 , and a second main function is to implement optimal configuration of energy, wherein photovoltaic energy is preferably used for power generation to ensure that output power of the photovoltaic cell array  10  is preferably used for the air conditioning unit  30 , and if there is no sufficient energy, the public grid  60  supplements energy. Preferably, the current conversion unit  20  is a four-quadrant current converter. 
     When the output power of the photovoltaic cell array  10  is higher than or equal to input power required by running of the air conditioning unit  30 , the direct current generated by the photovoltaic cell array  10  is inverted into alternating current for supply to the air conditioning unit through the first inverter module  31 , the air conditioning unit  30  is powered by the photovoltaic cell array  10  only, and is not required to be powered by the public grid  60 , and the current conversion unit  20  does not work. 
     When the output power of the photovoltaic cell array  10  is lower than the input power required by running of the air conditioning unit  30 , the direct current generated by the photovoltaic cell array  10  is transmitted to the first inverter module  31  for supply to the air conditioning unit  30 , commercial power is simultaneously rectified into direct current for transmission to the first inverter module  31  through the current conversion unit  20 , and the air conditioning unit is jointly powered by the public grid  60  and the photovoltaic cell array  10  to compensate for a shortcoming of photovoltaic power generation. 
     When the output power of the photovoltaic cell array  10  is higher than the input power required by running of the air conditioning unit  30 , or when the air conditioning unit  30  does not work, the current conversion unit  20  converts a part or all of the direct current output by the photovoltaic cell array into alternating current for transmission to the public grid  60  to implement grid-connected power generation. The current conversion unit  20  is independent of a controller of the air conditioning unit  30 , so grid-connected power generation may be implemented only by the photovoltaic cell array  10  under the condition that the air conditioning unit  30  is not started. 
     Preferably, the photovoltaic air conditioning system of the embodiment further includes a collector unit and a power distribution unit, and the photovoltaic cell array  10 , the photovoltaic collector unit, the power distribution unit and the second direct current bus-bar  50  are sequentially connected. 
     Preferably, the photovoltaic air conditioning system of the embodiment further includes a direct current step-up module, and the direct current step-up module is arranged between the power distribution unit and the second direct current bus-bar  50 . 
     In the embodiment, the air conditioning unit  30  is a central air conditioning unit and preferably a centrifugal water-cooled unit, a screw type water-cooled unit or a multi-connected air conditioning unit. 
     According to the photovoltaic air conditioning system provided by the embodiment, the air conditioning unit may be normally powered, and in addition, a type of the current conversion unit  20  may be freely selected according to a practical requirement without any limit of a factory equipment parameter of the air conditioning unit, so that applicability of the air conditioning unit is improved, the air conditioning unit may be matched with any photovoltaic power plant, and waste of electric energy of the photovoltaic power plant may be avoided. 
     Embodiment 2 
     The photovoltaic air conditioning system provided by embodiment 2 of the disclosure further includes a current conversion unit cooling device adopting a cooling manner such as air cooling, water cooling and coolant cooling. When the air cooling manner is adopted, the current conversion unit  20  is cooled by a radiator and a radiation fan. When a water cooling manner is adopted, the current conversion unit  20  is cooled by a water pump and a water circulating pipeline. 
     Preferably, the coolant cooling manner is adopted for cooling the current conversion unit. As shown in  FIG. 2 , the air conditioning unit  30  includes an evaporator  33 , first condenser  34 , compressor  35  and first throttling element  36  which are connected into a cooling circulation system. 
     The current conversion unit cooling device includes a coolant pump  61 , second throttling element  62  and heat exchanger (not shown in the figure) which are sequentially connected in series. A first end of the coolant pump  61  is communicated with the first condenser  34 , a second end is communicated with the second throttling element  62 , a first end of the heat exchanger is communicated with the second throttling element  62 , a second end is communicated with the evaporator  33 , the heat exchanger contacts with the current conversion unit  20 , and the current conversion unit  20  is cooled by heat exchange of the heat exchanger and the current conversion unit  20 , that is, the heat exchanger functions as a cooler. The second throttling element  62  may be one or a combination of multiple of a capillary tube, a thermal expansion valve, an electronic expansion valve and a throttling orifice plate. 
     Wherein, the heat exchanger is a metal cooling plate into which a coolant flow passage is embedded, the metal plate contacts with the current conversion unit, a proper cooling type may also be selected according to a factor such as a field environment condition and a shape and cooling requirement of the current conversion unit, and for example, for a device incapable of contact heat exchange or with a low cooling requirement, a finned tube heat exchanger, a plate-fin heat exchanger or the like may be adopted as a cooler. 
     The current conversion cooling device further includes a one-way valve  63 , the one-way valve  63  is arranged in parallel with the coolant pump  61 , an inlet of the one-way valve  63  is communicated with the first condenser  34 , and an outlet is communicated with the second throttling element  62 . Due to arrangement of the one-way valve  63 , backflow of a coolant and bypass short-circuit of the coolant may be prevented, and sufficient coolant for cooling a frequency converter may be ensured. By the coolant cooling manner, a remarkable cooling effect may be achieved, and a component type selection requirement may also be properly lowered. 
     The coolant may absorb a great amount of heat after flowing through the current conversion unit, and the heat may be finally accumulated into the coolant in the air conditioning unit to continuously increase system temperature and system pressure of the air conditioning unit in a shutdown state if not being released. If a cooling system works for a long time in the shutdown state of the air conditioning unit, the system temperature may be continuously increased to cause influence on the cooling effect of the current conversion unit, and the system pressure may be continuously increased to cause influence on safety of the whole cooling circulation system. Preferably, a second condenser  64  is arranged between the heat exchanger and the evaporator  33 , the low-temperature coolant flowing out of the second throttling element  62  absorbs heat dissipated by the current conversion unit at the cooler to be evaporator into high-temperature coolant vapor, the coolant vapor exchanges heat with air or water to be condensed into a liquid coolant again when flowing to the second condenser  64 , and the liquid coolant enters the evaporator  33 , and returns to the air conditioning unit to implement a cooling cycle. 
     A function of the second condenser  64  is to improve reliability of the system and enable the cooling system to normally work for a long time in the shutdown state of the air conditioning unit. In addition, when the air conditioning unit is started to work, the second condenser  64  may also prevent a great amount of heat from entering the evaporator  33  to reduce energy efficiency of the air conditioning system. The second condenser  64  usually adopts a finned tube heat exchanger or a plate heat exchanger. 
     When the current conversion unit  20  consists of multiple independent modules, multiple parallel heat exchange branches may be correspondingly arranged between the coolant pump  61  and the evaporator  33 , and a throttling element and one or more heat exchangers are arranged on each branch to cool each module. 
     The photovoltaic air conditioning system with the current conversion cooling device provided by the disclosure may implement cooling of an electronic power device under the conditions that the air conditioning unit is started and not started, so that the problem that the electronic power device may not be cooled if the air conditioning unit is not started in the conventional art is solved, cooling of the electronic power device in a photovoltaic power generation system is implemented under the condition that the air conditioning unit is not started, reliability of the photovoltaic system is improved, and in addition, service life of the air conditioning unit is prolonged. 
     From the above, the disclosure has the advantages that: adaptability to various photovoltaic power plants with different capacities may be achieved, and a photovoltaic power plant may be seamlessly and effectively combined with a heat ventilation air conditioner; and in addition, cooling of the electronic power device in the photovoltaic power generation system is implemented under the condition that the air conditioning unit is not started, reliability of the photovoltaic system is improved, and in addition, service life of the air conditioning unit is prolonged. 
     The abovementioned embodiments only represent some implementation modes of the invention, are specifically described in detail, but may not thus be understood as limits to the invention. It should be pointed out that those skilled in the art may also make various transformations and improvements without departing from the concept of the invention, and these transformations and improvements all fall within the scope of protection of the invention. Therefore, the scope of protection of the invention should be subject to the appended claims.