Low-cost and low-capacitance variable frequency driving system for central air conditioner

Abstract

The utility model discloses a low-cost and low-capacitance variable-frequency driving system for a central air conditioner, which is characterized in that a rectifier module is of a three-phase half-control rectifier structure formed by RBR / S / T thyristors, and an energy storage module is bridged between a direct-current output positive electrode and a direct-current output negative electrode of the RBR / S / T thyristors of the rectifier module through a thin-film capacitor; and the downstream of the thin-film capacitor is directly connected with the IGBT inversion module. Problems that the existing frequency converter is large in size, cannot be airborne and is high in cost are fully improved.

Description

Technical Field

[0001] The present application relates to the field of air conditioning frequency conversion technology, and in particular to a low-cost frequency conversion drive system for central air conditioning. Background Art

[0002] With the development of the economy, energy efficiency and environmental protection issues have received more and more attention. In order to save energy and reduce emissions and pursue energy efficiency, central air conditioners are increasingly tending to be variable frequency, and the application of frequency converters is increasing.

[0003] As the cooling capacity of central air conditioners increases, the power of the inverters used in the units is also increasing. The industry generally uses voltage-type inverters, and the energy storage link relies on electrolytic capacitors. The number of electrolytic capacitors is determined by the power of the inverter. Generally, the cost of electrolytic capacitors accounts for about 8% of the inverter cost, and the volume accounts for 20-30% of the inverter.

[0004] like Figure 1 As shown, the existing frequency conversion system mainly includes: circuit breaker QF1, rectifier module, DC reactor L, bypass contactor, starting resistor RES, capacitor C, voltage balancing resistor, inverter module; the existing solution has the following problems:

[0005] This solution results in a large inverter cabinet. In particular, when the current of an air-cooled inverter cabinet exceeds 800A, it cannot be installed onboard and can only be placed on the customer's site for installation. The installation and debugging process is complex, time-consuming and labor-intensive. At the same time, the inverter cabinet of this solution uses a bypass contactor, and the accompanying electrolytic capacitors are expensive. Utility Model Content

[0006] The technical problem to be solved by the present application is to provide a low-cost, low-capacitance variable frequency drive system for central air conditioning in view of the problem that existing frequency converters are large in size and cannot be mounted on airborne devices and are costly.

[0007] The embodiment of the present application is implemented as follows:

[0008] A low-cost, low-capacitor variable-frequency drive system for central air conditioning is characterized in that the rectifier module is a three-phase half-controlled rectifier structure composed of RBR / S / T thyristors, the energy storage module uses a thin-film capacitor connected across the DC output positive and negative poles of the RBR / S / T thyristors of the rectifier module; and the IGBT inverter module is directly connected downstream of the thin-film capacitor.

[0009] In the above technical solution, the thyristors of the rectifier modules RBR / S / T are respectively connected to the thyristor drive boards, and the thyristor drive boards are electrically connected to the control board.

[0010] In the above technical solution, a DC reactor series circuit is set between the thyristor of the rectifier module RBR / S / T and the film capacitor, a DCT1 Hall sensor is set in front of the DC reactor, and the positive electrode of the film capacitor is connected to the input side or left side of the DC reactor through the copper busbar through the center of the DCT1 Hall sensor. An FU1 fuse is set after the DC reactor, and the downstream of the FU1 fuse is directly connected to the positive electrode of the film capacitor.

[0011] In the above technical solution, in the rectifier module, the RBR / S / T thyristors are respectively arranged behind the three-phase circuit breaker.

[0012] In the above technical solution, the film capacitor is directly connected to the inverter module behind the jumper point without providing a voltage balancing resistor or a buffer resistor.

[0013] In the above technical solution, the withstand voltage range of the film capacitor is 800-1200V, preferably 300-1200V / 500-1200V / or 800-1000V / or 1000-1200V.

[0014] In the above technical solution, the minimum capacitance of the film capacitor C = P / 0.97*η*f*Umix2; where P is the output power, η is the efficiency, f is the input side frequency, and Umix is ​​the minimum effective value of the operating voltage.

[0015] In the above technical solution, the rectifier module is configured to slowly raise the voltage during the power-on stage.

[0016] In the above technical solution, when the film capacitor is powered on, it is set to be rectified first and then reach the C capacitor. The bus voltage rises slowly to achieve the capacitor filtering of the DC voltage and support the operation of the subsequent inverter.

[0017] In the above technical solution, the IU / V / WIGBT1 module is configured with the IU / V / WQ1 driver board to form an inverter module, and the output terminals U / V / W of the inverter module are connected to the motor.

[0018] Compared with the prior art, the beneficial effects of this application are:

[0019] 1. In the technical solution of the present application, film capacitors replace electrolytic capacitors. Film capacitors have good voltage resistance and do not require series capacitors to increase voltage resistance, so there is no need for equalizing resistors, and the cost of the electrical cabinet is low.

[0020] 2. Film capacitors replace traditional electrolytic capacitors. Film capacitors have good temperature resistance and small size, so the size of the inverter cabinet can be reduced.

[0021] 3. The use of film capacitors has good temperature resistance and voltage resistance, which improves the safety and stability of the inverter.

[0022] 4. Use film capacitors to replace traditional electrolytic capacitors, and cooperate with half-controlled rectifier circuits to eliminate the voltage-equalizing resistor, starting resistor and bypass contactor, reducing the size of the electrical cabinet and reducing costs.

[0023] 5. Design a new half-controlled rectifier circuit structure, do not use buffer resistors or starting resistors, and bypass contactors, reduce device instability, and improve inverter performance and lower cost.

[0024] 6. Design DC loop current detection, test DC current to control output side voltage, reduce the impact of bus ripple on capacitor heating, and better control capacitor temperature.

[0025] 7. Using a less-capacitor solution results in a smaller capacitor charging current and also reduces harmonic pollution on the grid side.

[0026] 8. Design DC circuit fuse to increase safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 This is a structural diagram of the existing variable frequency drive system in the prior art.

[0029] Figure 2 This is a structural diagram of a low-cost, low-capacitor variable-frequency drive system for a central air conditioner according to an embodiment of the present application.

[0030] Figure 3 RBR / S / T thyristor wiring diagram. Figure 3 The port assignments are as follows: Terminal 1: power input; Terminal 2: DC output positive pole; Terminal 3: DC output negative pole; K1 / G1: thyristor gate drive interface.

[0031] Figure 4 IU / V / WIGBT module wiring diagram. Figure 4 The port assignments are as follows: Terminal P: DC positive input; Terminal N: DC negative input; Terminal OUT: AC output; E / G1 / 2: IGBT drive interface. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0034] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0035] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of this application is typically placed when in use. These terms are intended only to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] Furthermore, terms such as "horizontal," "vertical," and "overhanging" do not necessarily imply that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0037] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0038] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0039] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0040] Example 1

[0041] like Figure 2-4 As shown, the low-cost, low-capacitance variable frequency drive system for central air conditioning implemented according to the utility model includes a QF1 circuit breaker 1, an RBR / S / T thyristor 2, a DCT1 Hall sensor 3, a C1~N capacitor 4, an L1 DC reactor 5, a FU1 fuse 6, a control board 7, a control line 8, a copper bus, an IU / V / WIGBT module 10, an IU / V / WC absorption capacitor 11, an IU / V / WQ drive board 12, a U / V / WCT Hall sensor 13, a thyristor drive board 14; a rectifier component 100, and an inverter component 200.

[0042] PM01 motor 15 is used to illustrate the solution: the patent is further described in detail below in conjunction with the accompanying drawings.

[0043] like Figure 2 As shown, the above circuit structure or driving system is divided into the following three working modules or working links:

[0044] Rectifier module 100: It is composed of three RBR / S / T thyristors 2 to form a three-phase half-controlled rectifier structure, connected behind the circuit breakers set respectively for the three phases, as a rectifier module;

[0045] The rectifier module 100 uses three-phase half-controlled rectification to convert the input AC power into DC power, and slowly raises the voltage during the power-on phase.

[0046] Public energy storage module: connected to the downstream of the rectifier module 100 through the DCT1 Hall sensor 3, L1 DC reactor 5, and FU1 fuse 6, using thin film capacitors C1~CN (C1~N capacitor 4);

[0047] When powered on, the public energy storage module is first rectified and then reaches the C capacitor. The bus voltage rises slowly, and the capacitor filters the DC voltage and supports the operation of the subsequent inverter.

[0048] A DCT1 Hall sensor 3 is provided before the L1 DC reactor 5 between the rectifier module 100 and the common energy storage module, and an FU1 fuse 6 is provided after the L1 DC reactor 5, so there is no need to worry about voltage breakdown.

[0049] Inverter module 200: IU / V / WIGBT1 module is configured with IU / V / WQ1 driver board 12 to form an inverter network module. Under the control of control board 7, DC power is output as frequency-adjustable AC power to U, V, and W terminals, and then output from U / V / W terminals to Figure 2 The PM01 motor 15 is not shown.

[0050] The control board 7 is a conventional controller in the prior art having IGBT inverter control functions and thyristor driving functions, and is connected to the system of the present invention in a conventional connection manner, which will not be described in detail.

[0051] The difference or the main innovation of the present invention from the prior art is that there is no multiple starting resistors or buffer resistors RES1-RES3 after the rectifier module 100, and the film capacitors C1~N capacitors 4 of the common energy storage module are connected only after the DCT1 Hall sensor 3, L1 DC reactor 5, and FU1 fuse 6, replacing Figure 1 Traditional electrolytic capacitors in.

[0052] Secondly, since thin film capacitors C1 to N4 are used, which have good withstand voltage performance and do not need to be connected in series to increase withstand voltage, the utility model does not need to set a voltage-equalizing resistor RVS between the inverter module 200 and the rectifier module 100. The cost of the electrical cabinet is low.

[0053] At the same time, film capacitors have good voltage resistance, eliminating the need for equalizing resistors, starting resistors and KM bypass contactors, reducing the size of the electrical cabinet and reducing costs.

[0054] Film capacitors have high voltage resistance, generally up to 1200V, while electrolytic capacitors generally withstand voltages of 400V or 450V, so they need to be used in series. To balance the voltage, a voltage-equalizing resistor is required. With film capacitors, there's no need to worry about voltage breakdown, and since they don't need to be used in series, a voltage-equalizing resistor isn't necessary.

[0055] Film capacitors have high corrosion resistance. Film capacitors are encapsulated in plastic, while electrolytic capacitors are placed in aluminum casings. They are not affected by corrosive environments, while electrolytic capacitors require special treatment.

[0056] Film capacitors have better high temperature and humidity working characteristics than electrolytic capacitors and can work normally in extreme environments, laying the foundation for reducing the size of electrical cabinets.

[0057] Film capacitors have an equivalent resistance (ESR) that is superior to that of electrolytic capacitors, with low heat loss. A single film capacitor can withstand higher ripple voltage than an electrolytic capacitor.

[0058] To sum up: For inverters with the same capacity, fewer film capacitors can be used to replace electrolytic capacitors.

[0059] The inverter uses film capacitors. The reduction of DC link capacitance will cause DC bus fluctuation problem. The solution of this utility model is as follows:

[0060] Minimum capacitance C = P / 0.97*η*f*Umix2; where P is the output power, η is the efficiency, f is the input frequency, and Umix is ​​the minimum operating voltage RMS value;

[0061] Calculate the minimum capacitor C using the above formula (DC bus ripple voltage △U = Vp * 0.3). Vp is the average grid voltage after three-phase bridge uncontrolled rectification, Vp ≈ 1.414 * grid-side line voltage RMS. For example, if the grid line voltage RMS is 380V, Vp ≈ 537V. When the grid voltage fluctuates, the Vp value also changes. Furthermore, based on this application, the output voltage duty cycle can be optimized based on the actual bus voltage and output voltage requirements to achieve the desired square wave inverter output.

[0062] in:

[0063] The right end of QF1 circuit breaker 1 is connected to port 1 of RBR / S / T thyristor 2 or the power input port using a copper busbar, such as Figure 3 ;

[0064] The output port 2 or DC output positive terminal of RBR / S / T thyristor 2 is connected to the positive electrode of C1~N capacitor 4 through a copper busbar; Figure 2 ;

[0065] The output port 3 of the RBR / S / T thyristor 2 or the negative electrode of the DC output is connected to the negative electrode of the C1~N capacitor 4 through a copper busbar; Figure 2 ;

[0066] The positive electrode of C1~N capacitor 4 is connected to the left side of L1 DC reactor 5 or Figure 2 the lower end;

[0067] The negative electrode of the C1~N capacitor 4 is connected to the input terminal N of the IU / V / WIGBT module 10 through a copper busbar; Figure 2 and Figure 4 As shown;

[0068] The IU / V / WQ driver board 12 is directly connected to the IU / V / WIGBT module 10, and the IGBT driver board pads are soldered to the IGBT contacts; Figure 2 ;

[0069] L1 DC reactor 5 is connected to the left end of FU1 fuse 6 through copper busbar; Figure 2 ;

[0070] The right end of the FU1 fuse 6 is connected to the input terminal P of the IU / V / WIGBT module 10 through a copper busbar; Figure 2 and Figure 4 As shown;

[0071] The IU / V / WC absorption capacitor 11 is connected between the P and N terminals of the IU / V / WIGBT module 10; Figure 2 Specifically, the IUC1 absorption capacitor is connected between the P and N terminals of the IU1 IGBT module 10; the IVC1 absorption capacitor is connected between the P and N terminals of the IVC1 IGBT module 10; and the IWC1 absorption capacitor is connected between the P and N terminals of the IGBT module 10.

[0072] The control board 7 is connected to the DCT1 Hall sensor 3, the IU / V / WQ driver board 12, the U / V / WCT Hall sensor 13, and the thyristor driver board 14 through the control line 8. Figure 2 ;

[0073] The output port OUT of the IU / V / WIGBT module 10 is connected to the PM01 motor 15 through the copper busbar through the U / V / WCT Hall sensor 13, as shown in Figure 2 .

[0074] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A low-cost, low-capacitance variable frequency drive system for central air conditioning, characterized in that: The rectifier module is a three-phase half-controlled rectifier structure composed of RBR / S / T thyristors. The energy storage module uses a thin film capacitor connected across the DC output positive and DC output negative poles of the RBR / S / T thyristors of the rectifier module; the IGBT inverter module is directly connected downstream of the thin film capacitor.

2. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1, characterized in that: The thyristors of the rectifier module RBR / S / T are respectively connected to the thyristor drive board, and the thyristor drive board is electrically connected to the control board.

3. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1, characterized in that: A DC reactor series circuit is set between the rectifier module RBR / S / T thyristor and the film capacitor. A DCT1 Hall sensor is set in front of the DC reactor. The positive electrode of the film capacitor is connected to the input side or left side of the DC reactor through the copper busbar through the center of the DCT1 Hall sensor. An FU1 fuse is set after the DC reactor, and the downstream of the FU1 fuse is directly connected to the positive electrode of the film capacitor.

4. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1, characterized in that: In the rectifier module, the RBR / S / T thyristors are respectively arranged behind the three-phase circuit breakers.

5. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1, characterized in that: The film capacitor jumper is directly connected to the inverter module without setting a voltage equalizing resistor or a buffer resistor.

6. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1, characterized in that: The withstand voltage range of film capacitors is 800-1200V.

7. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1 is characterized in that The withstand voltage range of film capacitors is 800-1000V or 1000-1200V.

8. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1 is characterized in that The minimum capacitance of a film capacitor is C=P / 0.97*η*f*Umix2; where P is the output power, η is the efficiency, f is the input frequency, and Umix is ​​the minimum effective value of the operating voltage.

9. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1 is characterized in that The rectifier module is set to slowly increase the voltage during the power-on phase.

10. The low-cost, low-capacitance variable frequency drive system for central air conditioning according to claim 1, characterized in that The IU / V / WIGBT1 module is configured with the IU / V / WQ1 driver board to form an inverter module. The inverter module output terminals U / V / W are connected to the motor.

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