power inverter parallel operation, not only to achieve power combining, and easy composition of building blocks, redundant, intelligent distributed large power supply network systems, power technology development direction. Fieldbus control technology can easily build a distributed inverter power controller area network, making the AC power system from the traditional centralized power supply mode to distributed power supply even intelligent power system development, system intelligent control effective means. This article describes a parallel power inverter based on CAN fieldbus, and take full advantage of TMS320LF2407A DSP chip, TI's internal resources, get and parse the scene from various parallel modules embedded CAN bus control data, in response to the scene strong real-time operation, dispatch monitoring module work,power inverter.
achieve, the key problem is that the power inverter share the load current to achieve the current run of the power inverter. Inverter power module parallel operation consisting of the AC power system, each module output AC signal, and thus, the parallel between them than the parallel operation of the DC power supply is much more complex. Power inverter in parallel to meet five conditions , that is the same as the voltage, frequency, waveform, phase and phase sequence, the only way to eliminate the circulation, load-sharing power, to achieve the best run state, and realize the inverter Power in parallel. The supply voltage amplitude and phase differences are caused by the current of the inverter power differences, synchronous operation and current output consistent Inverter Parallel control the ultimate solution to the problem. This design uses embedded CAN bus TMS320LF2407A DSP chip to achieve parallel synchronous operation of the power inverter and all flow.
3 DSP-based CAN bus design
based on CAN bus DSP control inverter parallel hardware design block diagram control such as 3-1. DSP based on sampling to obtain feedback value with the given value comparison, control output PWM pulse driving the bridge power switches, the output frequency, amplitude,Grid tie inverter,Grid tie inverter, phase adjustable sinusoidal voltage. CAN controller receives commands from the CAN bus control of parallel inverter power module.
Figure 3-1 System hardware structure
3.1 CAN bus hardware design
DSP chip TMS320LF2407A embedded in a CAN controller, CAN bus communication play an important role in the implementation of this article inverter parallel implementation, it provides for parallel operation synchronization signal as well as the current value of a given data transmission. With CAN bus interface must be accompanied by the the CAN bus receptor , DSP chip TMS320LF2407A 3.3V supply TI company specializes in a 3.3 V power supply 240x series DSP design three models CAN bus transceiver , that SN65HVD230, SN65HVD231 SN65HVD232. They are based on a 3.3 V power supply can be connected up to 120 nodes on the bus, and the temperature rises to a certain value,, the bus automatically shut down, electric or removed node to other nodes on the bus did not affect the family of devices supports transfer rates up to 1Mbps. In this system is the choice of the SN65HVD232 as CAN receptors, pinout shown in Figure 3-2. Pin 1 (D) is used to send data pin 4 (R) for receiving data, they should be connected to the the DSP chip CANTX/IOP6 and CANTX/IOP7.
CAN communication between the two DSP
In order to further improve the anti-jamming capability, using the high-speed optocoupler 6N137 constitute isolation circuit shown in Figure 3-3,3-4 shown. 6N137 High Speed Optocoupler the CAN network speed can reach the speed of the driver and the resistor network . The data transmission the isolation the figure CANTX and data receive isolation circuit CANRX are pin on the DSP, CANTX CAN send data pin, CANRX CAN receive data pin circuit R1 is a current limiting resistor optocoupler 6N137 input current can not be less than 7.5mA; resistor R2 is a pull-up resistor; the resistor R3 matched resistors at both ends of the CAN bus network, select the 120Ω resistor , the matching resistance plays a very important role, they are ignored, will anti-jamming system data communication greatly reduce or even not work,power inverter.
3.2 CAN bus software design
the indisputable master of the master-slave control strategy of parallel inverter power system communication design. All the synchronizing signal from the module, the current instantaneous amplitude of the reference take autonomous module. In order to adapt to the requirements of the parallel redundant, to avoid the main module failure resulting in paralysis of the entire system, and the main module is dynamically established. Certain intervals, each module must broadcast a the contention master "request, and if it is not already established in the master module, or" the contention master "request module has already established the main module of the fault is first issued and can become a new master module. Using the indisputable main principle of master-slave control, in the case of a main module failure by the other from modules competition to become the main module, instead of the original master module status, this mechanism can ensure that the entire system will not be because of a communication master node paralysis caused by paralysis of the entire inverter module communication system .
common LED drive circuit analyzes this paper important electronic fever Friends Network. The buck circuit capacitor is a common small-current power circuit, because of their sizes small, cost is low, the current is constant absolute strengths are often applied to the LED drive circuit. Figure 1 for the the actual take capacitance buck LED driver circuit. Careful and utilize local convergence varistor or transient voltage restraint transistor circuit, Initiative connection on varistor or transient voltage system made transistor voltage gradient moment (such as lightning, electricity equipment starting) effectively gradient current discharge, thus maintaining two shut with the other transistor, the response time of the individual micro-millisecond. circuit works: of capacitor C1 for the buck with limited flow: As we all know, the characteristics of the capacitor is through exchange, every DC, When the capacitor convergence in exchange circuit, its capacitance calculations formula: XC = 1/2πf C , XC performance capacitive reactance, f performance input AC power frequency, C represents the buck capacitor. flows through the capacitor step-down circuit current calculations formula: I = U / XC where I said that the current flowing through the capacitor, said power supply voltage U, XC, said the capacitance of the capacitor when the load voltage is much less than 220V, 220V, 50Hz AC circuit, the current and capacitance relational : I = 69C wherein the capacitor unit is uF, the current in units of mA following table for 220V, 50Hz AC circuit current of practice with actual measuring current analogy the resistor R1 is the bleeder resistor, and its role as follows: When the sine wave at the maximum peak instant been intercepted, the residual charge on the capacitor C1 helpless release, long long existence in the repair if the human body is exposed to C1 of the metal sector strong electric shock may be the presence of resistor R1 residual charge can release let go, in order to protect human, machine insurance. Bleed resistor and capacitor size, the greater the capacity of the normal capacitor more remnants charge, bleeder resistor on the resistance would choose. Lessons following table, for the design of reference: The role of D1 ~ D4 is rectified, its role is the AC power is rectified to a pulsating DC voltage. The role of the C2, C3 for the filter,power inverter, its role is the rectified pulsating DC voltage into a stable DC voltage filtering. Varistor (or transient voltage system made transistor) the role of the input pulse high-voltage power supply in an instant on release let go, which cover LED transient high voltage breakdown. Depending on the number of LED series may be forward breakover voltage (Vf), 220V AC circuits, can be up to about 80. component selection of the capacitor voltage is individual requests greater than the peak value of the input supply voltage, 220V, 50Hz AC circuit, the trade-offs withstand voltage of 400 volts or more polyester capacitors or paper media capacitor. D1 ~ D4 can choose IN4007. The filter capacitor C2, C3 of the breakdown voltage according to the load voltage, Common to 12 times the load voltage. Its capacitance depending on the size of the load current. driver circuit capacitor buck following schematic other situations, for design reference: in the circuit of Figure 2, the thyristor SCR and R3 maintenance circuit, when the flow through the LED current is greater than the set value, the SCR conduction a certain angle, so the circuit current shunt, so that LED working in constant current situation, to prevent the LED from damage due to high-voltage transient. composed of low-level power supply filtering circuit circuit in Figure 3, C1, R1, varistors, L1, R2, able to enter an instant high-pressure filter composed of step-down circuit,Grid tie inverter, C2, R2, C3, C4, L2, and pressure sensitive resistor is composed of a filter circuit rectified. This circuit take dual filter circuit to cover the LED is not an instant high-voltage breakdown destruction. Figure 4 is a schematic capacitance antihypertensive use circuit, the application of two anti-parallel LED circuit for rectifying an AC voltage after the buck, can be generally applied to the luminous lights, buttons instigation lamp request not high the status of guidance lights and other places.
due to the performance of these machines has been greatly reduced, inevitably there are a variety of ills, and after-sales service of these machines is relatively less than perfect. Plus machines scattered, standardize the management of the second-hand excavator market has been a very troublesome problem facing the industry.
January 14 this year, the Ministry of Commerce issued a "notice" legacy excavator imported message switching application materials, eight aspects of this policy on second-hand excavator engine exhaust emissions, the driver ear noise, etcpower inverter. made strictly regulate old excavator quality problems trying to source control, in order to protect the overall quality of imported second-hand excavator.
The author of
single control source, can not effectively solve all the ills of the two mobile phones. Circulation, service, repair, scrap can not be ignored.
Although prices have hit a discount, but the price of second-hand excavator is still quite high, the user at the time of purchase if you encounter problems, to withstand losses is still subject to a lot of these machines circulation and trading issues should also be fully attention. Must establish an effective security system, so that consumers' interests are protected. sale stage in the new machineGrid tie inverter, these machines have enjoyed the after-sales and maintenance services, two phone trade again, unable to enjoy the same maintenance and after-sale protection can be obtained from the manufacturer when purchased with a new machine. The manufacturers can not this part of the machine is included in the routine maintenance and after-sale protection program. This responsibility is often unilateral falls on the dealer the shoulders. A reference to "the old excavator warranty period of not less than three months or 500 hours (whichever occurs first), the important parts (engines, pumps, motors, valves, hydraulic imported second-hand excavator acceptance cylinders and other hydraulic components) for 6 months or 1000 hours (whichever comes first). imported old excavator operators need to provide consumers with warranty include content have been or are about to enter two phone requires frequent maintenance stage, such a short time to repair is not enough. I believe that part of the OEMs in China has a wholly-owned or joint venture enterprises, these enterprises should assume corresponding responsibility to reach a corresponding agreement with the dealer to receive a portion of the cost of some products get better service.
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