Disclosure of Invention
The invention provides a parallel direct-current power supply system for solving the problems, and the direct-current power supply system obtains direct-current bus voltage through DC/DC boosting of a single storage battery, is used for improving the reliability of the direct-current system and achieves the purpose of stably supplying power to an in-station protection device.
According to some embodiments, the invention adopts the following technical scheme:
a parallel type direct current power supply system comprises an alternating current power distribution unit, wherein the alternating current power distribution unit is connected with a parallel type power supply conversion module, the parallel type power supply conversion module is connected with a load through a direct current output bus, and the load is connected with a monitoring module through closed loop feedback;
the parallel power conversion module comprises a plurality of parallel power conversion assemblies, each power conversion assembly comprises a power conversion module and a storage battery, each power conversion module comprises an AC/DC converter, the input end of each AC/DC converter is connected with an alternating current power distribution unit, the output end of each AC/DC converter is respectively connected with the input end of a charging DC/DC voltage reduction circuit and the input end of a DC/DC circuit, the output end of each charging DC/DC voltage reduction circuit is respectively connected with the input ends of the storage battery and a discharging DC/DC voltage boosting circuit, the output end of each discharging DC/DC voltage boosting circuit and the output end of each DC/DC circuit are connected with the input end of a filter circuit, and the output end of each filter circuit is connected with a direct current output bus.
Furthermore, each power conversion module comprises a CPU, the CPU is respectively connected with an AC/DC converter, a charging DC/DC voltage reduction circuit, a discharging DC/DC voltage boosting circuit, a DC/DC circuit, the CPU, a filter circuit and a storage battery, and the storage battery is grounded.
Furthermore, each power conversion module is connected in parallel by a CAN bus.
Furthermore, the negative end of the parallel power conversion module is connected with the cathode of a first overload freewheeling diode, the anode of the first overload freewheeling diode is connected with a first overload freewheeling fuse, and the first overload freewheeling fuse is connected with a total output direct current bus.
Furthermore, the positive terminal of the parallel power conversion module is connected with the anode of a second overload freewheeling diode, the cathode of the first overload freewheeling diode is connected with a second overload freewheeling fuse, and the second overload freewheeling fuse is connected with a total output direct current bus.
Furthermore, the parallel power supply conversion module is connected with the direct current insulation monitoring device through a total output direct current bus.
Furthermore, the direct current insulation monitoring device is connected with the monitoring module.
Furthermore, each power conversion module is connected with a power element, each power element is connected in parallel by a CAN bus, and the power elements are used for adjusting the voltage of each power conversion module and equalizing the current.
Furthermore, the parallel power conversion module is connected with the intelligent module and used for managing charging and discharging of the storage battery, floating charging at regular time, temperature compensation and capacity monitoring.
Furthermore, the on-line core capacity is realized by setting a manual starting state or an automatic state through the monitoring module.
Compared with the prior art, the invention has the beneficial effects that:
the invention adopts the parallel battery technology, the damage or open circuit of a single battery does not affect the operation of the system, and the device has the online capacity checking function, can identify the damaged storage battery in time, greatly enhances the reliability of the direct current power supply system and improves the safe operation level of a power grid.
The specific implementation mode is as follows:
the invention is further described with reference to the following figures and examples.
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
In the present invention, terms such as "connected" and "connecting" should be interpreted broadly, and mean either directly or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be determined according to specific situations by persons skilled in the relevant scientific or technical field, and are not to be construed as limiting the present invention.
Example one
The present embodiment provides a parallel type dc power supply system, as shown in fig. 1.
A parallel type direct current power supply system comprises an alternating current power distribution unit, wherein the alternating current power distribution unit is connected with a parallel type power supply conversion module, the parallel type power supply conversion module is connected with a load through a direct current output bus, and the load is connected with a monitoring module through closed loop feedback;
the parallel power conversion module comprises a plurality of parallel power conversion assemblies, each power conversion assembly comprises a power conversion module and a storage battery, each power conversion module comprises an AC/DC converter, the input end of each AC/DC converter is connected with an alternating current power distribution unit, the output end of each AC/DC converter is respectively connected with the input end of a charging DC/DC voltage reduction circuit and the input end of a DC/DC circuit, the output end of each charging DC/DC voltage reduction circuit is respectively connected with the input ends of the storage battery and a discharging DC/DC voltage boosting circuit, the output end of each discharging DC/DC voltage boosting circuit and the output end of each DC/DC circuit are connected with the input end of a filter circuit, and the output end of each filter circuit is connected with a direct current output bus.
Specifically, as shown in fig. 2, the operating principle of the parallel dc power supply system is as follows: a single 12V storage battery (string) is connected with a power supply conversion module to form a parallel power supply assembly, and the direct-current high-voltage output ends of similar multi-assembly modules are connected in parallel to form a direct-current power supply bus. The power conversion module in the system comprises an AC/DC rectification circuit, a storage battery charging DC/DC voltage reduction circuit, a storage battery discharging DC/DC voltage boosting circuit and the like, and a special DSP (Digital Signal Processing) chip is used for acquisition, calculation and control.
Each power conversion module comprises a CPU, the CPU is respectively connected with an AC/DC converter, a charging DC/DC voltage reduction circuit, a discharging DC/DC voltage boosting circuit, a DC/DC circuit, the CPU, a filter circuit and a storage battery, and the storage battery is grounded. Each power conversion module is connected in parallel by a CAN bus. The negative pole end of the parallel power supply conversion module is connected with the cathode of a first overload follow current diode, the anode of the first overload follow current diode is connected with a first overload follow current fuse, and the first overload follow current fuse is connected with a total output direct current bus. And the positive end of the parallel power supply conversion module is connected with the anode of a second overload freewheeling diode, the cathode of the first overload freewheeling diode is connected with a second overload freewheeling fuse, and the second overload freewheeling fuse is connected with a total output direct current bus.
The parallel power supply conversion module is connected with the direct current insulation monitoring device through a total output direct current bus; the direct-current insulation monitoring device is connected with the monitoring module.
Each power conversion module is connected with one power element, the power elements are connected in parallel by adopting a CAN bus, and the power elements are used for adjusting the voltage of each power conversion module and equalizing the current. The parallel power supply conversion module is connected with the intelligent module and is used for managing charging and discharging of the storage battery, floating charging at regular time, temperature compensation and capacity monitoring. And the monitoring module is set to be in a manual starting state or an automatic state, so that the online capacity checking is realized.
In order to implement the above functions, the following technical solutions are adopted in this embodiment:
(1) system overload and feeder short circuit isolation technology
Fig. 3 reflects the working principle of the overload freewheeling circuit of the system. In the parallel direct current system, all current needs to be output through the parallel power supply conversion module, so that the problem of matching between module protection and external protection electrical appliances exists. Currently, this problem is solved mainly by two aspects: overload output characteristics of the power conversion module; and the external series connection accumulator overload follow current circuit.
The structure that each branch battery in a parallel direct-current power supply system is completely isolated from an alternating-current bus and a direct-current bus and other branch batteries is utilized, a plurality of 12V batteries lower than the voltage of the direct-current bus are connected in parallel, and the batteries are connected with the direct-current bus through a discharge diode and a protection fuse. The series battery pack has only a discharge path to the dc bus. When the power supply works normally, the parallel power supply module with the voltage stabilizing function carries the load; when the system is overloaded or has short-circuit fault, the parallel power supply module still supplies current, and if the voltage of the direct current bus is reduced to the voltage of the series battery pack, the series battery pack supplies follow current.
(2) Online automatic capacity checking technology
The parallel direct current technology provides physical conditions for one-to-one management of the single storage batteries, and the single storage batteries can be discharged according to a general 10-hour discharge rate (0.1C10, wherein C10 is 10h rate rated capacity (Ah)) to realize automatic online full-capacity check capacity.
After the system is put into operation, the check sexual discharge function is defaulted to be closed, and the function is started through the monitoring module. The manual start or automatic state can be set by monitoring. And in the process of the core capacity, the alternating current is powered off, the system maintains the core capacity until the end, and when the condition is not met in the process of the core capacity, the core capacity is continued after the jump. And the system is immediately transferred to be uniformly charged after the capacity checking is finished, and is in floating charge after the uniform charging is finished, so that the capacity checking data can be exported through monitoring.
(3) Digital current sharing techniques
Figure 4 reflects the digital current sharing principle of operation of the system. Since the output of the system is voltage source in nature, small deviations in the output voltage can result in large differences in output current, which if not equalized, can result in an inability to reasonably distribute the system load.
The main reason why the parallel operation of the power elements requires current sharing is that, because the output of the power conversion module is of a voltage source nature, a small deviation of the output voltage can cause a large difference of the output current, and if the current sharing is not the same, the module cannot reasonably distribute the system load. The traditional analog mode has the problems that the current sharing degree is poor when the line impedance is high, the current sharing quantity of the modules is small, the offline modules are difficult to quit the current sharing and the like, so that the current sharing of the modules is influenced. However, with the digital development of module power supplies, the current sharing of the CAN bus is widely applied.
The CAN bus digital current sharing method adopted by the embodiment CAN prolong the average service life of each module and improve the consistency of the discharge time of each battery under the alternating current accident. Through information interaction of the CAN bus, a one-master multi-slave mode is adopted, so that the amplitude of voltage of each module is adjusted, and the current sharing of the modules is finally realized. Wherein the address determination of the CAN be determined by the dial switch of the power module and the CAN propagation rate defaults to 125 Kbps. Each power element broadcasts its own address and local CAN state on the CAN bus after power up. The CAN bus CAN be determined several seconds after the power element is electrified, the number of the slave lines CAN be determined by the CAN bus, the average current is calculated, and then the average current is sent to each slave line; the power element adjusts the voltage of the circuit of the element to perform current equalization. The CAN bus only carries out operation and does not carry out current sharing. And after the current of the slave line is completely adjusted, the residual current is naturally distributed to the CAN bus. The current equalizing instruction issued by the CAN bus is that the average current is subtracted from the current of the CAN bus to be used as an instruction, after the current equalizing instruction is received from a line, if the current of the line is larger than the average current, the current equalizing ring of the line subtracts the actual current from the average current, and then the current equalizing ring and the actual current are subjected to proportional integral adjustment (PI adjustment), so that the final adjustment output quantity of the current equalizing ring is a negative value and is superposed on a voltage ring, the voltage instruction is reduced, and the output voltage is finally reduced through closed-loop adjustment of a feedback loop. In addition, the power module set as the core capacity does not need to participate in current sharing, and can dynamically and automatically quit current sharing regulation after receiving a core capacity instruction issued by monitoring.
(4) Intelligent management technology
The intelligent module in the parallel direct current power supply component can carry out fine management on each storage battery monomer, and the fine management comprises the following steps: battery charge and discharge management, timing uniform floating charge management, temperature compensation, capacity monitoring, various perfect protection and the like. When the power supply conversion module and the monitoring connection are in a failure state, managing the battery according to default parameters; and under the condition of being effectively connected with the monitoring, managing the battery according to the monitoring setting parameters.
The invention successfully solves the problems that the degradation of a single section of the series storage battery affects the performance of the whole battery pack and the full-capacity check of the storage battery pack is difficult to carry out on line, and the like, enhances the reliability of a direct-current power supply system and improves the safe operation level of a power grid.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.