Power distribution system with double-feeder voltage sag compensation function

Abstract

The utility model discloses a power distribution system with a double-feeder voltage sag compensation function. The power distribution system comprises a first alternating-current bus, a second alternating-current bus, a super capacitor, a first inversion quick-release assembly, a second inversion quick-release assembly, a charging assembly and a charging and discharging controller, the input end and the output end of the super capacitor are electrically connected with the input end of the first inversion fast-discharging assembly, the input end of the second inversion fast-discharging assembly and the output end of the charging assembly respectively, and the output end of the first inversion fast-discharging assembly is electrically connected with the power grid side of the first alternating-current bus. The output end of the second inversion quick discharge assembly is electrically connected with the power grid side of the second alternating current bus, and the input end of the charging assembly is electrically connected with the load side of the first alternating current bus or the second alternating current bus. According to the utility model, the two phase lines share the super capacitor as an energy supply unit, electric energy can be quickly fed into the alternating current bus by virtue of the cooperation of the super capacitor and the inversion quick discharge, the control is simple, the equipment cost is low, and the adaptability is strong.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of power distribution technology, especially to a power distribution system with double feed line voltage sag compensation function. BACKGROUND

[0002] In 10kV rural power network, the voltage sag problem at the end of the line often affects the stability of power supply and the safe operation of rural power network. This problem can be caused by many factors and has a wide range of influence. For example, there is usually a large load fluctuation in rural power network users, such as the switching operation of irrigation, breeding and other electrical equipment, which will cause instantaneous load change, especially during the peak period of electricity consumption, which may cause voltage sag at the end.

[0003] To this end, the existing scheme is mostly to realize voltage compensation for a single feeder, and the commonly used device is dynamic voltage restorer (DVR). When the system voltage sags, DVR injects AC voltage of the same frequency as the system to offset the change of system voltage. The amplitude of the injected voltage is the difference between normal voltage and fault voltage. Although DVR can better realize voltage sag compensation, when voltage sag occurs in two feeders, the additional inverter device will increase the investment cost.

[0004] In addition, the energy of the conventional DVR compensation voltage is provided by the DC side. Due to the factors such as battery internal resistance and chemical reaction efficiency, the traditional DC energy storage unit may cause additional energy loss when providing power support, affecting the overall system efficiency. For occasions where voltage sag occurs frequently, the charging speed of the battery may not meet the demand of rapid recovery. Although some high-performance batteries (such as lithium batteries) have good discharge rate, traditional lead-acid batteries and some other types of batteries perform poorly in terms of discharge rate and cannot provide enough current to meet the rapidly changing voltage demand in a short time. UTILITY MODEL CONTENTS

[0005] The technical problem to be solved by the utility model is to provide a power distribution system with double feed line voltage sag compensation function, which realizes double feed line voltage sag compensation while reducing equipment cost and improving response speed.

[0006] In order to solve the above technical problems, the utility model adopts the technical scheme of:

[0007] A power distribution system with double feed line voltage sag compensation function, comprising a first AC bus, a second AC bus, a super capacitor, a first inverter fast discharge component, a second inverter fast discharge component, a charging component and a charge and discharge controller.

[0008] The input and output ends of the super capacitor are respectively electrically connected with the input end of the first inverter fast discharge assembly, the input end of the second inverter fast discharge assembly and the output end of the charging assembly, the output end of the first inverter fast discharge assembly is electrically connected with the grid side of the first alternating current bus, the output end of the second inverter fast discharge assembly is electrically connected with the grid side of the second alternating current bus, and the input end of the charging assembly is electrically connected with the load side of the first alternating current bus or the second alternating current bus.

[0009] The charging and discharging controller is respectively electrically connected with the control end of the first inverter fast discharge assembly, the control end of the second inverter fast discharge assembly and the control end of the charging assembly.

[0010] Further, the first inverter fast discharge assembly comprises a first three-phase inverter and a first transformer.

[0011] The DC side of the first three-phase inverter is electrically connected with the input and output end of the super capacitor, the AC side of the first three-phase inverter is electrically connected with the low-voltage side of the first transformer, and the high-voltage side of the first transformer is connected in series with the grid side of the first alternating current bus.

[0012] The control end of the first three-phase inverter is electrically connected with the charging and discharging controller.

[0013] Further, the second inverter fast discharge assembly comprises a second three-phase inverter and a second transformer.

[0014] The DC side of the second three-phase inverter is electrically connected with the input and output end of the super capacitor, the AC side of the second three-phase inverter is electrically connected with the low-voltage side of the second transformer, and the high-voltage side of the second transformer is connected in series with the grid side of the second alternating current bus.

[0015] The control end of the second three-phase inverter is electrically connected with the charging and discharging controller.

[0016] Further, the charging assembly comprises a single-phase rectifier and a third transformer.

[0017] The DC side of the single-phase rectifier is electrically connected with the input and output end of the super capacitor, the AC side of the single-phase rectifier is electrically connected with the low-voltage side of the third transformer, and the high-voltage side of the third transformer is connected in parallel with the load side of the first alternating current bus or the second alternating current bus.

[0018] The control end of the single-phase rectifier is electrically connected with the charging and discharging controller.

[0019] Further, the low-voltage side of the first transformer is connected in parallel with a first reactive compensation capacitor.

[0020] Further, the low voltage side of the second transformer is connected in parallel with a second reactive compensation capacitor.

[0021] Further, the first three-phase inverter and the second three-phase inverter are both bridge inverters.

[0022] Further, the single-phase rectifier is a bridge rectifier.

[0023] Further, the AC side of the first three-phase inverter and the AC side of the second three-phase inverter are both connected in series with a first inductor.

[0024] Further, the AC side of the single-phase rectifier is connected in series with a second inductor.

[0025] The power distribution system with double feed line voltage sag compensation function has the advantages that the double feed line voltage sag compensation circuit is connected between the first AC bus and the second AC bus, the super capacitor can compensate the voltage of the first AC bus and the second AC bus through the first inverter fast discharge component and the second inverter fast discharge component, the common super capacitor is used as an energy supply unit, the equipment investment is reduced, the super capacitor and the inverter fast discharge component are combined to quickly feed the electric energy into the AC bus, the slow charging of the super capacitor by the AC bus and the charging component can avoid the problem of load imbalance, the control is simple, the equipment cost is low, and the adaptability is high. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 It is a circuit connection schematic view of the power distribution system with double feed line voltage sag compensation function.

[0027] Fig. 2 It is a component schematic view of the first three-phase inverter or the second three-phase inverter of the power distribution system with double feed line voltage sag compensation function.

[0028] Fig. 3 It is a component schematic view of the single-phase rectifier of the power distribution system with double feed line voltage sag compensation function.

[0029] LABEL EXPLANATION

[0030] AC1, first AC bus; AC2, second AC bus;

[0031] C1, first reactive compensation capacitor; C2, second reactive compensation capacitor; CP, super capacitor;

[0032] L1, first inductor; L2, second inductor;

[0033] T1, first transformer; T2, second transformer; T3, third transformer; TB, single-phase rectifier;

[0034] U1, first three-phase inverter; U2, second three-phase inverter. DETAILED DESCRIPTION

[0035] To illustrate the technical content of the utility model, the purposes and effects achieved, the following will be described in conjunction with the embodiments and the accompanying drawings.

[0036] Please refer to Figs. 1 to 3 A power distribution system with double-fed line voltage sag compensation function, comprising a first AC bus AC1, a second AC bus AC2, a super capacitor CP, a first inverter fast discharge assembly, a second inverter fast discharge assembly, a charging assembly and a charge-discharge controller.

[0037] The input and output ends of the super capacitor CP are respectively electrically connected with the input end of the first inverter fast discharge assembly, the input end of the second inverter fast discharge assembly and the output end of the charging assembly, the output end of the first inverter fast discharge assembly is electrically connected with the grid side of the first AC bus AC1, the output end of the second inverter fast discharge assembly is electrically connected with the grid side of the second AC bus AC2, and the input end of the charging assembly is electrically connected with the load side of the first AC bus AC1 or the second AC bus AC2.

[0038] The charge-discharge controller is respectively electrically connected with the control end of the first inverter fast discharge assembly, the control end of the second inverter fast discharge assembly and the control end of the charging assembly.

[0039] From the above description, the utility model has the beneficial effect that the double-fed line voltage sag compensation circuit is connected between the first AC bus AC1 and the second AC bus AC2, which is composed of a super capacitor CP, a first inverter fast discharge assembly, a second inverter fast discharge assembly, a charging assembly and a charge-discharge controller. The super capacitor CP can compensate the voltage of the first AC bus AC1 and the second AC bus AC2 through the first inverter fast discharge assembly and the second inverter fast discharge assembly respectively to cope with the voltage sag problem occurring on the first AC bus AC1 and the second AC bus AC2. The super capacitor CP is used as a power supply unit to reduce equipment investment. The super capacitor CP and the inverter fast discharge assembly can quickly feed power into the AC bus. The super capacitor CP has high charge-discharge power and relatively low stored energy. The slow charging of the super capacitor CP by the AC bus and the charging assembly does not easily cause load imbalance. The control is simple, the equipment cost is low, and the adaptability is strong.

[0040] Further, the first inverter fast discharge assembly comprises a first three-phase inverter U1 and a first transformer T1;

[0041] The DC side of the first three-phase inverter U1 is electrically connected with the input and output end of the super capacitor CP, the AC side of the first three-phase inverter U1 is electrically connected with the low-voltage side of the first transformer T1, and the high-voltage side of the first transformer T1 is connected in series with the grid side of the first AC bus AC1.

[0042] The control end of the first three-phase inverter U1 is electrically connected with the charge and discharge controller.

[0043] Further, the second inverter fast discharge assembly comprises a second three-phase inverter U2 and a second transformer T2;

[0044] The DC side of the second three-phase inverter U2 is electrically connected with the input and output end of the super capacitor CP, the AC side of the second three-phase inverter U2 is electrically connected with the low-voltage side of the second transformer T2, and the high-voltage side of the second transformer T2 is connected in series with the grid side of the second AC bus AC2.

[0045] The control end of the second three-phase inverter U2 is electrically connected with the charge and discharge controller.

[0046] From the above description, it can be seen that the first inverter fast discharge assembly and the second inverter fast discharge assembly are both composed of a three-phase inverter and a transformer. The three-phase inverter converts the DC voltage output by the super capacitor CP into an AC voltage, and then the transformer performs voltage boosting. Finally, the AC bus is fed in. By controlling the three-phase inverter, the super capacitor CP can quickly release the stored electrical energy at a high current, thereby maintaining the stability of the grid voltage.

[0047] Further, the charging assembly comprises a single-phase rectifier TB and a third transformer T3;

[0048] The DC side of the single-phase rectifier TB is electrically connected with the input and output end of the super capacitor CP, the AC side of the single-phase rectifier TB is electrically connected with the low-voltage side of the third transformer T3, and the high-voltage side of the third transformer T3 is connected in parallel with the load side of the first AC bus AC1 or the second AC bus AC2.

[0049] The control end of the single-phase rectifier TB is electrically connected with the charge and discharge controller.

[0050] From the above description, the charging assembly includes a single-phase rectifier TB and a third transformer T3, the output of the third transformer T3 is converted into a direct current voltage by the single-phase rectifier TB and output to the super capacitor CP, by controlling the working parameters of the single-phase rectifier TB, low-current slow charging can be realized, so that the system as a whole realizes slow charging and fast discharging, reasonably manages charging and discharging, can reduce heat and power loss, realizes high energy density and power density, and can improve the stability of the system and prolong the service life of the super capacitor CP.

[0051] Further, the low-voltage side of the first transformer T1 is connected in parallel with a first reactive compensation capacitor C1.

[0052] Further, the low-voltage side of the second transformer T2 is connected in parallel with a second reactive compensation capacitor C2.

[0053] From the above description, the reactive compensation capacitor is connected to the low-voltage side of the transformer, which can effectively suppress the magnetizing inrush current, and to a certain extent, perform reactive compensation, reduce the reactive power demand of the system, improve the power factor, reduce the burden on the power grid, and save electricity costs.

[0054] Further, the first three-phase inverter U1 and the second three-phase inverter U2 are both bridge inverters.

[0055] From the above description, the three-phase inverter part adopts a bridge inverter circuit, which has the advantages of high efficiency, simple structure, stability and reliability, and good adaptability to changes in grid load.

[0056] Further, the single-phase rectifier TB is a bridge rectifier.

[0057] From the above description, the single-phase rectifier TB is a bridge rectifier, which has high rectification efficiency, simple structure and low cost.

[0058] Further, the AC side of the first three-phase inverter U1 and the AC side of the second three-phase inverter U2 are both connected in series with a first inductor L1.

[0059] Further, the AC side of the single-phase rectifier TB is connected in series with a second inductor L2.

[0060] From the above description, the inductors are arranged on the AC sides of the inverters and the rectifiers, which play a filtering role, eliminate noise interference in the circuit, and make the output current more stable.

[0061] Please refer to Figs. 1 to 3 The embodiment one of the utility model discloses:

[0062] The power distribution system with double-fed line voltage sag compensation function comprises a first AC bus AC1, a second AC bus AC2, a super capacitor CP, a first inverter fast discharge assembly, a second inverter fast discharge assembly, a charging assembly and a charge-discharge controller; the input and output ends of the super capacitor CP are electrically connected with the input ends of the first inverter fast discharge assembly and the second inverter fast discharge assembly and the output end of the charging assembly respectively, the output end of the first inverter fast discharge assembly is electrically connected with the grid side of the first AC bus AC1, the output end of the second inverter fast discharge assembly is electrically connected with the grid side of the second AC bus AC2, and the input end of the charging assembly is electrically connected with the load side of the first AC bus AC1 or the second AC bus AC2; the charge-discharge controller is electrically connected with the control ends of the first inverter fast discharge assembly, the second inverter fast discharge assembly and the charging assembly respectively.

[0063] In the embodiment, the operation process of the power distribution system with double-fed line voltage sag compensation function comprises:

[0064] The double-fed line is formed on the first AC bus AC1 and the second AC bus AC2, when voltage sag occurs in one of the first AC bus AC1 and the second AC bus AC2, the corresponding first inverter fast discharge assembly or second inverter fast discharge assembly is controlled to make the super capacitor CP output electric energy to the AC bus where voltage sag occurs, complete voltage sag compensation, and through reasonable load distribution, load balance can be realized between the first AC bus AC1 and the second AC bus AC2 of the power grid, so as to avoid voltage reduction caused by excessive load of a certain line. When the load demand at the end of the power grid is high, the double-fed line can automatically switch the circuit or adjust the power transmission line according to the real-time load change, so as to ensure that the end voltage remains within the standard range. At the same time, when the voltages of the first AC bus AC1 and the second AC bus AC2 are normal, the charging assembly is used to charge the super capacitor CP, so as to cope with the next voltage compensation demand.

[0065] In the embodiment, the first inverter fast discharge assembly comprises a first three-phase inverter U1 and a first transformer T1; the DC side of the first three-phase inverter U1 is electrically connected with the input and output end of the super capacitor CP, the AC side of the first three-phase inverter U1 is electrically connected with the low-voltage side of the first transformer T1, the high-voltage side of the first transformer T1 is connected in series with the grid side of the first AC bus AC1; and the control end of the first three-phase inverter U1 is electrically connected with the charge and discharge controller. The second inverter fast discharge assembly comprises a second three-phase inverter U2 and a second transformer T2; the DC side of the second three-phase inverter U2 is electrically connected with the input and output end of the super capacitor CP, the AC side of the second three-phase inverter U2 is electrically connected with the low-voltage side of the second transformer T2, the high-voltage side of the second transformer T2 is connected in series with the grid side of the second AC bus AC2; and the control end of the second three-phase inverter U2 is electrically connected with the charge and discharge controller. The charging assembly comprises a single-phase rectifier TB and a third transformer T3; the DC side of the single-phase rectifier TB is electrically connected with the input and output end of the super capacitor CP, the AC side of the single-phase rectifier TB is electrically connected with the low-voltage side of the third transformer T3, the high-voltage side of the third transformer T3 is connected in parallel with the load side of the first AC bus AC1 or the second AC bus AC2; and the control end of the single-phase rectifier TB is electrically connected with the charge and discharge controller.

[0066] In addition, the low-voltage side of the first transformer T1 is connected in parallel with a first reactive compensation capacitor C1. The low-voltage side of the second transformer T2 is connected in parallel with a second reactive compensation capacitor C2.

[0067] Preferably, as shown in Fig. 2 and Fig. 3 The first three-phase inverter U1 and the second three-phase inverter U2 are both bridge inverters. The single-phase rectifier TB is a bridge rectifier. The AC side of the first three-phase inverter U1 and the AC side of the second three-phase inverter U2 are both connected in series with a first inductor L1. The AC side of the single-phase rectifier TB is connected in series with a second inductor L2.

[0068] In summary, the power distribution system with double-fed line voltage sag compensation function provided by the utility model has the advantages that the double-fed line voltage sag compensation circuit is connected between the first AC bus and the second AC bus, the double-fed line voltage sag compensation circuit is composed of a super capacitor, a first inverter fast discharge assembly, a second inverter fast discharge assembly, a charging assembly and a charge and discharge controller, the super capacitor can perform voltage compensation on the first AC bus and the second AC bus through the first inverter fast discharge assembly and the second inverter fast discharge assembly respectively, so as to cope with voltage sag problems occurring on the first AC bus and the second AC bus, the super capacitor is used as a power supply unit, equipment investment is reduced, electric energy can be rapidly fed into the AC bus by means of the cooperation of the super capacitor and the inverter fast discharge assembly, the characteristics of the super capacitor, i.e., high charge and discharge power and relatively low stored energy, are utilized, the super capacitor is slowly charged by means of the AC bus and the charging assembly, load imbalance is not easily caused, control is simple, equipment cost is low, and the adaptability is strong.

[0069] The above merely illustrates the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent transformation or direct or indirect application in the related technical field based on the content of the present application specification and drawings is also included in the patent protection scope of the present application.

Claims

1. A power distribution system with dual-feeder voltage sag compensation function, characterized in that, The first AC bus, the second AC bus, the super capacitor, the first inverter fast discharge assembly, the second inverter fast discharge assembly, the charging assembly and the charge-discharge controller are included. The input and output ends of the super capacitor are respectively electrically connected with the input ends of the first inverter fast discharge assembly, the input ends of the second inverter fast discharge assembly and the output end of the charging assembly, the output end of the first inverter fast discharge assembly is electrically connected with the grid side of the first AC bus, the output end of the second inverter fast discharge assembly is electrically connected with the grid side of the second AC bus, and the input end of the charging assembly is electrically connected with the load side of the first AC bus or the second AC bus. The charge-discharge controller is respectively electrically connected with the control ends of the first inverter fast discharge assembly, the second inverter fast discharge assembly and the charging assembly.

2. The power distribution system having a dual-feed line voltage sag compensation function according to claim 1, characterized by, The first inverter fast discharge assembly includes a first three-phase inverter and a first transformer. The DC side of the first three-phase inverter is electrically connected with the input and output ends of the super capacitor, the AC side of the first three-phase inverter is electrically connected with the low-voltage side of the first transformer, and the high-voltage side of the first transformer is connected in series with the grid side of the first AC bus. The control end of the first three-phase inverter is electrically connected with the charge-discharge controller.

3. The power distribution system with dual-feeder voltage sag compensation function according to claim 2, characterized in that, The second inverter fast discharge assembly includes a second three-phase inverter and a second transformer. The DC side of the second three-phase inverter is electrically connected with the input and output ends of the super capacitor, the AC side of the second three-phase inverter is electrically connected with the low-voltage side of the second transformer, and the high-voltage side of the second transformer is connected in series with the grid side of the second AC bus. The control end of the second three-phase inverter is electrically connected with the charge-discharge controller.

4. The power distribution system having a dual-feed voltage sag compensation function according to claim 1, characterized by, The charging assembly includes a single-phase rectifier and a third transformer. The DC side of the single-phase rectifier is electrically connected with the input and output ends of the super capacitor, the AC side of the single-phase rectifier is electrically connected with the low-voltage side of the third transformer, and the high-voltage side of the third transformer is connected in parallel with the load side of the first AC bus or the second AC bus. The control end of the single-phase rectifier is electrically connected with the charge-discharge controller.

5. The power distribution system with dual feed voltage sag compensation function according to claim 2, characterized in that, The low-voltage side of the first transformer is connected in parallel with a first reactive compensation capacitor.

6. The power distribution system having a dual-feed voltage sag compensation function according to claim 3, characterized by, The low-voltage side of the second transformer is connected in parallel with a second reactive compensation capacitor.

7. The power distribution system having a dual-feed voltage sag compensation function according to claim 3, characterized by, The first three-phase inverter and the second three-phase inverter are both bridge inverters.

8. The power distribution system having a dual-feed voltage sag compensation function according to claim 4, characterized by, The single-phase rectifier is a bridge rectifier.

9. The power distribution system having a dual-feed voltage sag compensation function according to claim 3, characterized by, The AC side of the first three-phase inverter and the AC side of the second three-phase inverter are both connected in series with a first inductor.

10. The power distribution system having a dual-feed voltage sag compensation function according to claim 4, characterized by, The AC side of the single-phase rectifier is connected in series with a second inductor.

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