Hybrid reactive power compensation device based on SVG and capacitor bank

Abstract

The utility model discloses a mixed reactive power compensation device based on an SVG and a capacitor bank, which provides fixed reactive power compensation by arranging an intelligent capacitor bank, and dynamically compensates residual reactive power on the basis that the intelligent capacitor bank compensates the fixed reactive power. The characteristics that the intelligent capacitor bank is low in unit capacity cost but low in response speed and the SVG is high in response speed but high in unit capacity cost are taken into consideration, the intelligent capacitor bank and the SVG work cooperatively, large-capacity compensation of the intelligent capacitor bank is achieved, and the functions of rapid compensation and harmonic suppression of the SVG are achieved. Therefore, the electric energy quality of a power utilization environment is improved, the power factor of a power grid is obviously improved, the compensation range is wide, the compensation function is diversified, the response speed is high, the cost is low, the economic benefit is obvious, and accurate tracking of rapidly-changed reactive power can be met so as to improve the voltage flicker phenomenon.

Description

Technical Field

[0001] The utility model relates to the technical field of low-voltage power distribution, in particular to a reactive power compensation device, in particular to a hybrid reactive power compensation device based on SVG and a capacitor group. Background Art

[0002] There are a lot of reactive loads in the power system, such as transmission lines, transformers, asynchronous motors, and arc furnaces, which consume reactive power. The existence of reactive power has many disadvantages, increasing the loss of lines and equipment, occupying the capacity of lines and equipment, forming voltage drops on lines and equipment, and causing voltage stability problems. In order to reduce the adverse effects of reactive power, the principle of "layered and zoned, on-site compensation" was proposed, and some reactive power compensation equipment was put into operation one after another.

[0003] Since traditional capacitor parallel compensation can only compensate for inductive reactive power and cannot be adjusted continuously or achieve stepless compensation, the capacitor can only input or remove all reactive power to compensate for fixed reactive power. Even if the fixed value is changed by changing the number of switching groups, this reactive power compensation has no continuity. Reactive power compensation technology is transitioning from traditional capacitor parallel compensation to SVG technology.

[0004] The so-called SVG is a static reactive generator, which usually refers to a device that uses a self-commutated power semiconductor bridge inverter to perform dynamic reactive compensation. Compared with traditional capacitor parallel compensation, SVG has a faster adjustment speed and a wider operating range. Moreover, after taking measures such as multiplexing, multi-level or PWM technology, it can greatly reduce the content of harmonics in the compensation current. However, if SVG is used alone to compensate for system reactive power, although the problem of fast response is solved, the capacity that SVG can compensate is generally small. If you want to obtain a larger capacity compensation range, you need to connect multiple platforms of SVG to the grid, which is costly. Utility Model Content

[0005] In order to solve the technical problems existing in the background technology, the utility model proposes a hybrid reactive power compensation device based on SVG and capacitor bank.

[0006] The purpose of the utility model can be achieved through the following technical solutions:

[0007] The hybrid reactive power compensation device based on SVG and capacitor bank includes:

[0008] A detection module is connected to the low-voltage bus of the distribution transformer to detect voltage and current signals of a nonlinear load connected to the low-voltage bus in real time;

[0009] Smart capacitor banks, connected in parallel to the low-voltage busbars of distribution transformers, provide fixed reactive power compensation to nonlinear loads;

[0010] The first SVG is connected in parallel to the low-voltage busbar of the distribution transformer, and dynamically compensates for the remaining reactive power of the nonlinear load on the basis of the fixed reactive power compensation of the intelligent capacitor bank;

[0011] The first controller is communicatively connected to the detection module, the first SVG and the intelligent capacitor bank to identify the reactive power of the nonlinear load according to the phase difference between the voltage and the current detected by the current detection module, and control the intelligent capacitor bank and the first SVG to work in coordination.

[0012] Furthermore, the intelligent capacitor group specifically includes: a second controller and multiple groups of one-to-one corresponding switching switches, capacitors, and reactors. The switching switches, capacitors, and reactors are connected in series and then in parallel to the low-voltage bus of the distribution transformer. The second controller is communicated with the first controller and the switching switches respectively to control the on and off of the multiple groups of switching switches according to the control instructions of the first controller, and the fixed reactive power of the compensation is transformed by changing the number of switching groups.

[0013] Furthermore, the first SVG includes:

[0014] The inverter circuit is connected in parallel to the low-voltage busbar of the distribution transformer to generate or absorb reactive current and perform dynamic reactive compensation for non-linear loads;

[0015] The third controller is communicatively connected to the first controller and the inverter circuit to output a PWM pulse signal according to a control instruction of the first controller to control the on and off of the IGBT on the inverter circuit so as to adjust the reactive current outputted by the AC side of the inverter circuit.

[0016] The output filter is connected in series between the inverter circuit and the low-voltage bus to filter out the high-order harmonics generated by the switching of IGBTs in the reactive current generated by the inverter circuit.

[0017] Furthermore, the inverter circuit includes an inverter, a contactor S1, a capacitor C1 and a pre-charging branch, the positive pole of the inverter is connected to one end of the contactor S1, the other end of the contactor S1 is connected to the positive pole of the capacitor C1, the negative pole of the inverter is connected to the negative pole of the capacitor C1, and the pre-charging branch is connected in parallel at both ends of the contactor S1.

[0018] Furthermore, the pre-charging branch is formed by connecting a diode D1 and a charging resistor R1 in series, and the anode of the diode D1 is connected to the anode of the inverter.

[0019] Furthermore, the inverter adopts a three-phase bridge inverter.

[0020] Furthermore, the output filter adopts an LCRLL type output filter.

[0021] Furthermore, the hybrid reactive power compensation device further comprises:

[0022] The second SVG is connected in series with the circuit breaker and then in parallel with the low voltage busbar of the distribution transformer;

[0023] The first controller is respectively connected to the circuit breaker and the second SVG for controlling the circuit breaker to close when the first SVG fails, connecting the second SVG in parallel to the low-voltage busbar of the distribution transformer, and dynamically compensating for the remaining reactive power of the nonlinear load.

[0024] Furthermore, the first controller adopts a DSP chip.

[0025] Furthermore, the detection module includes an AC voltage transformer and an AC current transformer.

[0026] Beneficial effects of the utility model: the hybrid reactive power compensation device based on SVG and capacitor group proposed by the utility model provides fixed reactive power compensation by setting up intelligent capacitor group, and sets SVG to dynamically compensate the remaining reactive power on the basis of the intelligent capacitor group compensating the fixed reactive power, taking into account the characteristics of low unit capacity cost but slow response speed of intelligent capacitor group and fast response speed but high unit capacity cost of SVG, and making use of each other's strengths to make up for each other's weaknesses, and making the intelligent capacitor group work together with SVG, which not only realizes large-capacity compensation of intelligent capacitor group, but also realizes the functions of fast compensation and harmonic control of SVG, thereby improving the power quality of power consumption environment and significantly improving the power factor of power grid, and has the characteristics of wide compensation range, diversified compensation functions, fast response speed, low cost and obvious economic benefits, and can meet the precise tracking of fast-changing reactive power to improve voltage flicker phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a system schematic diagram of the utility model.

[0028] Figure 2 This is a system schematic diagram of the intelligent capacitor bank of the utility model.

[0029] Figure 3 It is a system schematic diagram of the first SVG of the utility model.

[0030] Figure 4 The single-phase equivalent circuit diagram of the LCRLL type output filter of the utility model. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0032] like Figure 1 As shown, the utility model provides a hybrid reactive power compensation device based on SVG and capacitor bank, comprising: a detection module, an intelligent capacitor bank, a first SVG, a first controller, a second SVG and a circuit breaker.

[0033] The detection module is connected to the low-voltage bus of the distribution transformer to detect the voltage and current signals of the nonlinear load connected to the low-voltage bus in real time, wherein the detection module includes an AC voltage transformer and an AC current transformer.

[0034] Smart capacitor banks, connected in parallel to the low-voltage busbar of the distribution transformer, provide fixed reactive power compensation to non-linear loads.

[0035] Among them, Figure 2 As shown, the intelligent capacitor bank specifically includes: a second controller and multiple groups of one-to-one corresponding switching switches, capacitors, and reactors. The switching switches, capacitors, and reactors are connected in series and then in parallel to the low-voltage bus of the distribution transformer. The second controller is communicated with the first controller and the switching switches respectively to control the on and off of the multiple groups of switching switches according to the control instructions of the first controller, and the fixed reactive power of the compensation is transformed by changing the number of switching groups.

[0036] The first SVG is connected in parallel to the low-voltage busbar of the distribution transformer, and dynamically compensates for the remaining reactive power of the nonlinear load on the basis of the fixed reactive power compensation of the intelligent capacitor bank.

[0037] The first controller is communicatively connected to the detection module, the first SVG and the intelligent capacitor bank to identify the reactive power of the nonlinear load according to the phase difference between the voltage and the current detected by the current detection module, and control the intelligent capacitor bank and the first SVG to work in coordination.

[0038] Specifically, the first controller adopts a DSP chip, wherein the function of the DSP chip is to complete A / D conversion, operation of command signals, processing of feedback signals, and generation of control instructions.

[0039] The detection module sends the voltage and current signals to the first controller for A / D conversion. The first controller processes and calculates the collected voltage and current signals, and identifies the reactive power of the nonlinear load based on the phase difference between the voltage and the current. Specifically, when the current and voltage are in phase, it means that the electric energy is completely converted into active power. When the current and voltage are inconsistent in phase, it means that the electric energy is partially converted into reactive power, and the reactive power that needs to be compensated is calculated.

[0040] When the reactive power to be compensated is small, the first controller first controls the first SVG to quickly compensate the required reactive power. As the nonlinear load connected to the low-voltage bus increases, the reactive power to be compensated increases. When the reactive power to be compensated exceeds the capacity of a single group of capacitors in the intelligent capacitor bank, the first controller immediately controls the intelligent capacitor bank to put in a group of capacitors to provide fixed reactive power compensation, and controls the first SVG to compensate for the remaining reactive power. When the nonlinear load connected to the low-voltage bus further increases, the reactive power to be compensated further increases. The first controller controls the first SVG to dynamically compensate for more remaining reactive power. When the reactive power compensated by the first SVG exceeds the capacity of a single group of capacitors in the intelligent capacitor bank again, the first controller controls the intelligent capacitor bank to put in another group of capacitors. By analogy, whenever the reactive power compensated by the first SVG exceeds the capacity of a single group of capacitors in the intelligent capacitor bank, the intelligent capacitor bank puts in a group of capacitors, thereby reducing the workload of the first SVG, thereby obtaining a larger and more responsive compensation range. When the nonlinear load connected to the low-voltage bus decreases, the first controller first controls the first SVG to offset the excess reactive power compensated by the smart capacitor bank. When the offset excess reactive power exceeds the capacity of a single capacitor bank in the smart capacitor bank, the first controller immediately controls the smart capacitor bank to remove a group of capacitors that have already been put into operation. When the nonlinear load connected to the low-voltage bus further decreases and the excess reactive power offset by the first SVG exceeds the capacity of a single capacitor bank in the smart capacitor bank again, the first controller controls the smart capacitor bank to immediately remove another group of capacitors that have been put into operation, and so on, until the smart capacitor bank removes all capacitors that have already been put into operation.

[0041] The second SVG is connected in series with the circuit breaker and then connected in parallel to the low-voltage bus of the distribution transformer. The first controller is respectively connected to the circuit breaker and the second SVG for communication, so that when the first SVG fails, the circuit breaker is controlled to close, and the second SVG is connected in parallel to the low-voltage bus of the distribution transformer, so that the remaining reactive power of the nonlinear load continues to be dynamically compensated through the second SVG.

[0042] like Figure 3 As shown, the first SVG and the second SVG use the same device, which specifically includes:

[0043] The inverter circuit is connected in parallel to the low-voltage busbar of the distribution transformer to generate or absorb reactive current and perform dynamic reactive compensation for non-linear loads.

[0044] The third controller is communicatively connected to the first controller and the inverter circuit to output a PWM pulse signal according to a control instruction of the first controller to control the on and off of the IGBT on the inverter circuit so as to adjust the reactive current outputted by the AC side of the inverter circuit.

[0045] The output filter is connected in series between the inverter circuit and the low-voltage bus to filter out the high-order harmonics generated by the switching of IGBTs in the reactive current generated by the inverter circuit.

[0046] The inverter circuit includes an inverter, a contactor S1, a capacitor C1 and a pre-charging branch. The positive pole of the inverter is connected to one end of the contactor S1, the other end of the contactor S1 is connected to the positive pole of the capacitor C1, the negative pole of the inverter is connected to the negative pole of the capacitor C1, the pre-charging branch is connected in parallel at both ends of the contactor S1, and the pre-charging branch is formed by a diode D1 and a charging resistor R1 connected in series. The positive pole of the diode D1 is connected to the positive pole of the inverter. The inverter adopts a three-phase bridge inverter.

[0047] Specifically, the contactor S1 is in a normally open state. At the moment when the hybrid reactive power compensation device is powered on and before the first SVG / second SVG starts to operate, since the contactor S1 is disconnected, the inverter pre-charges the capacitor C1 through the diode D1 and the charging resistor R1. After a delay of about 10 seconds, when the pre-charging is completed, the voltage across the capacitor C1 reaches about 530V. At this time, the third controller issues an instruction to close the contactor S1, and the diode D1 and the charging resistor R1 of the pre-charging branch are bypassed. The first SVG / second SVG begins to enter a normal operating state, thereby reducing or eliminating the impact current of the SVG DC side capacitor at the moment when the device is powered on, avoiding damage to the IGBT due to instantaneous short-circuit current, and ensuring the safety and reliability of the device when it starts to operate.

[0048] Since the inverter uses PWM technology, its output current contains not only the current used to compensate for reactive power, but also the higher harmonics generated by the on-off of IGBT. The high-frequency electromagnetic induction generated by this higher harmonic has a significant impact on control, communication equipment, and precision instruments, and will also bring additional losses to power transmission and distribution equipment (such as transmission lines, transformers, etc.). These additional higher harmonics enter the bus and are shunted by the power grid and loads, generating harmonic components in the public electrical environment and at the user's receiving end, causing serious pollution to both the power supply and the user. The output filter uses an LCRLL output filter, which can filter out the higher harmonics generated by the on-off of the power switching device in the compensation current generated by the inverter. Its single-phase equivalent circuit diagram is shown below: Figure 4 As shown in the figure, the LCRLL output filter has a series inductor L on the inverter side. 01 To ensure the reactive current compensation capability, a series inductor L is designed on the grid side. O2 Improve the filtering effect of high-order harmonic current.

[0049] The above contents are merely examples and explanations of the structure of the utility model. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the utility model or exceed the scope defined in the claims, they should all fall within the protection scope of the utility model.

Claims

1. A hybrid reactive power compensation device based on SVG and capacitor bank, characterized in that: include: A detection module is connected to the low-voltage bus of the distribution transformer to detect voltage and current signals of a nonlinear load connected to the low-voltage bus in real time; Smart capacitor banks, connected in parallel to the low-voltage busbars of distribution transformers, provide fixed reactive power compensation to nonlinear loads; The first SVG is connected in parallel to the low-voltage busbar of the distribution transformer, and dynamically compensates for the remaining reactive power of the nonlinear load on the basis of the fixed reactive power compensation of the intelligent capacitor bank; The first controller is communicatively connected to the detection module, the first SVG and the intelligent capacitor bank to identify the reactive power of the nonlinear load according to the phase difference between the voltage and the current detected by the current detection module, and control the intelligent capacitor bank and the first SVG to work in coordination.

2. The hybrid reactive power compensation device according to claim 1, characterized in that: The intelligent capacitor bank specifically includes: a second controller and multiple groups of one-to-one corresponding switching switches, capacitors, and reactors. The switching switches, capacitors, and reactors are connected in series and then in parallel to the low-voltage bus of the distribution transformer. The second controller is communicated with the first controller and the switching switches respectively to control the on and off of the multiple groups of switching switches according to the control instructions of the first controller, and the fixed reactive power of the compensation is transformed by changing the number of switching groups.

3. The hybrid reactive power compensation device according to claim 1, characterized in that: The first SVG includes: The inverter circuit is connected in parallel to the low-voltage busbar of the distribution transformer to generate or absorb reactive current and perform dynamic reactive compensation for non-linear loads; A third controller, which is communicatively connected to the first controller and the inverter circuit, outputs a PWM pulse signal to control the on-off of the IGBT on the inverter circuit according to the control instruction of the first controller, so as to adjust the reactive current outputted by the AC side of the inverter circuit; The output filter is connected in series between the inverter circuit and the low-voltage bus to filter out the high-order harmonics generated by the switching of IGBTs in the reactive current generated by the inverter circuit.

4. The hybrid reactive power compensation device according to claim 3, characterized in that: The inverter circuit includes an inverter, a contactor S1, a capacitor C1 and a pre-charging branch. The positive pole of the inverter is connected to one end of the contactor S1, the other end of the contactor S1 is connected to the positive pole of the capacitor C1, the negative pole of the inverter is connected to the negative pole of the capacitor C1, and the pre-charging branch is connected in parallel at both ends of the contactor S1.

5. The hybrid reactive power compensation device according to claim 4, characterized in that: The pre-charging branch is formed by connecting a diode D1 and a charging resistor R1 in series, and the anode of the diode D1 is connected to the anode of the inverter.

6. The hybrid reactive power compensation device according to claim 4, characterized in that: The inverter adopts a three-phase bridge inverter.

7. The hybrid reactive power compensation device according to claim 3, characterized in that: The output filter uses an LCRLL type output filter.

8. The hybrid reactive power compensation device according to claim 1, characterized in that: Also includes: The second SVG is connected in series with the circuit breaker and then in parallel with the low voltage busbar of the distribution transformer; The first controller is respectively connected to the circuit breaker and the second SVG for controlling the circuit breaker to close when the first SVG fails, connecting the second SVG in parallel to the low-voltage busbar of the distribution transformer, and dynamically compensating for the remaining reactive power of the nonlinear load.

9. The hybrid reactive power compensation device according to claim 1, characterized in that: The first controller adopts a DSP chip.

10. The hybrid reactive power compensation device according to claim 1, characterized in that: The detection module includes an AC voltage transformer and an AC current transformer.

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