Reactive power compensation device

Abstract

The utility model provides a reactive power compensation device, and relates to the technical field of power grid reactive power compensation. The device comprises a controller, a plurality of groups of compensation units and a trigger unit, the controller is connected with the trigger unit, and the trigger unit is connected with the plurality of compensation units; the trigger unit is connected with the compensation unit through an optical fiber, and electrical connection does not exist. The controller calculates reactive power needing to be compensated by detecting the voltage and current of the power grid of the power supply, and judges the group of compensation units needing to be input or cut off according to the reactive power needing to be compensated; and the trigger unit controls the compensation unit needing to input or cut off the power grid to perform reactive compensation on the power grid. According to the device, the thyristor is adopted to switch the capacitor, and the non-impact capacitor switching is realized by controlling the on and off of the thyristor, so that the power grid cannot be impacted even if the capacitor is switched frequently.

Description

Technical Field

[0001] The utility model relates to the technical field of reactive power compensation for power grids, in particular to a reactive power compensation device. Background Art

[0002] When the alternating current in the power grid passes through pure resistance, the electrical energy is converted into heat energy. When it passes through pure capacitive or pure inductive loads, no work is done, that is, no electrical energy is consumed, that is, reactive power. Of course, the actual load cannot be a pure capacitive load or a pure inductive load. It is generally a mixed load. In this way, when the current passes through the load, part of the electrical energy does not do work, and the power factor at this time is less than 1. In order to reduce the loss of transformers and transmission lines, improve the power factor of the power grid, and improve the power supply environment, a reactive compensation device is generally connected in parallel to the power grid to compensate for the fundamental reactive power and harmonics of the user bus. In the existing power system, because the load of the power grid often changes, reactive compensation is required. Dynamic reactive compensation refers to the instantaneous switching method. The switching capacitor group completes a full action within about 10-20 milliseconds. This control method cannot be achieved by mechanically acting contactors. The existing dynamic reactive compensation device has a large impact on the power grid, which may damage the capacitor and cause failures, and has high economic costs. Moreover, traditional reactive power compensation devices use programmable array logic and general array logic as core control devices, which are not only high in cost, high in power consumption, and low in efficiency, but also have poor scalability and small storage capacity, and cannot meet the needs of the development of flexible alternating current transmission systems (FACTS). Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a reactive power compensation device to achieve reactive power compensation of a power grid in view of the deficiencies of the above-mentioned prior art.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is: a reactive power compensation device, including a controller, multiple compensation units and a trigger unit; the controller is connected to the trigger unit, and the trigger unit is connected to multiple compensation units; the trigger unit is connected to the compensation unit by optical fiber, and there is no electrical connection; the controller calculates the reactive power that needs to be compensated by detecting the voltage and current of the power grid, and determines the group of compensation units that need to be put into or removed according to the reactive power that needs to be compensated; the trigger unit controls the compensation unit that needs to be put into or removed from the grid to perform reactive compensation on the grid.

[0005] Preferably, the controller comprises: a signal sampling device, an analog-to-digital converter, a complex programmable logic device, a memory, a power driving board and a power unit;

[0006] The signal sampling device is connected to the power grid and is used to collect current signals and voltage signals of the power grid through a Hall current sensor and a Hall voltage sensor, and output them to an analog-to-digital converter;

[0007] The analog-to-digital converter is connected to the signal sampling device, and is used to convert the current signal and voltage signal output by the signal sampling device into digital information, and output it to the complex programmable logic device;

[0008] The complex programmable logic device is connected to the analog-to-digital converter, and is used to analyze the digital information output by the analog-to-digital converter, obtain reactive power information, and output a driving signal to the power driving board according to the reactive power information;

[0009] The memory is connected to the complex programmable logic device and is used to store all data input by the complex programmable logic device;

[0010] The power driving board is connected to the complex programmable logic device, and is used to encode the driving signal output by the complex programmable logic device, generate a trigger pulse signal, and output it to the power unit to control the opening and closing of the power device in the power unit;

[0011] The power unit is connected to the power driving board and is used to generate the required compensation current by turning on and off the power device and output it to the power grid.

[0012] Preferably, the switching device in the power unit is an insulated gate bipolar transistor.

[0013] Preferably, the reactive power compensation device further comprises a serial communication device connected to the complex programmable logic device, for completing data transmission between the complex programmable logic device and the monitoring station.

[0014] Preferably, the compensation unit comprises a capacitor and a power electronic switch, and the power electronic switch comprises a thyristor and a diode; the thyristor and the diode are connected in reverse parallel, and the thyristor and the diode are electrically connected to the capacitor respectively.

[0015] Preferably, the reactive power compensation device comprises three compensation units, the three compensation units form a triangle connection structure, the three compensation units are connected end to end in sequence, and are connected to three live wires of the power grid through three conductors.

[0016] Preferably, the reactive power compensation device comprises three compensation units, the three compensation units form a ring connection structure, the three compensation units are connected end to end in sequence to form a closed loop, and are connected to three live wires of the power grid through three conductors.

[0017] Preferably, the compensation unit includes a capacitor, a power electronic switch and a reactor, the power electronic switch includes a thyristor and a diode; the thyristor and the diode are respectively connected to the reactor, and the reactor is connected to the capacitor, so that the reactor is connected in series between the capacitor and the power electronic switch.

[0018] Preferably, the multiple compensation units in the reactive power compensation device adopt a unitized structure and a modular design, and each unit includes a capacitor, a reactor and a power electronic switch, forming a system in itself; each module structural unit adopts a drawer-type structure.

[0019] The beneficial effects of adopting the above technical solution are: a reactive power compensation device provided by the utility model is connected in parallel to the power grid, and the compensation current can change quickly following the change of the reactive current of the load, automatically compensating the reactive power required by the power grid system, with low power consumption, high compensation efficiency, large storage capacity and low cost; and the power electronic switch of the compensation unit is used to switch the capacitor into the power grid for reactive power compensation when the voltage and current of the power grid are consistent with the voltage and current of the capacitor, so that the impact on the power grid is small, the capacitor is not damaged, the switching is convenient and the response time is short.

[0020] The utility model provides a low-voltage dynamic reactive power compensation device, which adopts thyristor switching capacitors and realizes impact-free switching of capacitors by controlling the switching on and off of the thyristors. Even if the capacitors are frequently switched on and off, no impact will be caused to the power grid. When the load of the power grid changes rapidly, the reactive power compensation device can also quickly track and respond, and the response time can be within 20 milliseconds. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A structural block diagram of a reactive power compensation device provided in Example 1 of the utility model;

[0022] Figure 2 A schematic diagram of a compensation unit of a reactive power compensation device provided in Example 1 of the utility model;

[0023] Figure 3 A schematic diagram of a compensation unit of a reactive power compensation device provided in Embodiment 2 of the present utility model;

[0024] Figure 4 A schematic diagram of a compensation unit of a reactive power compensation device provided in Embodiment 3 of the present utility model;

[0025] Figure 5 This is a schematic diagram of the drawer-type structure of the reactive power compensation device provided in Example 5 of the utility model.

[0026] In the figure: 100, capacitor; 200, power electronic switch; 210, thyristor; 220, diode; 300, reactor; 11, three wires; 12, three live wires of the power grid; 20, drawer-type structure. DETAILED DESCRIPTION

[0027] The following is a further detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0028] Embodiment 1:

[0029] In this embodiment, a reactive power compensation device, such as Figure 1 As shown, it includes a controller, multiple compensation units and a trigger unit; the controller is connected to the trigger unit, and the trigger unit is connected to the compensation unit; the trigger unit is connected to the compensation unit by optical fiber, and there is no electrical connection; the controller calculates the reactive power that needs to be compensated by detecting the voltage and current of the power grid, and determines the group of compensation units that need to be put into or removed according to the reactive power that needs to be compensated; the trigger unit controls the compensation unit that needs to be put into or removed from the grid to perform reactive compensation on the grid.

[0030] The controller includes: a signal sampling device, an analog-to-digital (A / D) converter, a complex programmable logic device (CPLD), a memory, a power driving board, a power unit and a serial communication device.

[0031] The signal sampling device is connected to the power grid and is used to collect the current signal and voltage signal of the power grid and output them to the analog-to-digital converter. In this embodiment, in order to accurately complete reactive power compensation for the power grid, the signal sampling device detects the power grid voltage and power grid current in real time through the Hall current sensor and the Hall voltage sensor.

[0032] The analog-to-digital converter is connected to the signal sampling device and is used to convert the current signal and voltage signal output by the signal sampling device into digital information and output it to the complex programmable logic device. After the analog-to-digital converter converts the received current signal and voltage signal into digital information, it can be digitally processed by the complex programmable logic device.

[0033] The complex programmable logic device is connected to the analog-to-digital converter, and is used to analyze the digital information output by the analog-to-digital converter, obtain reactive power information, and output a driving signal to the power driving board according to the reactive power information. The complex programmable logic device will quickly calculate the reactive power according to the grid current and grid voltage in the digital information, and calculate the phase shift angle of the output voltage of the power unit accordingly, and output a driving signal to the power driving board at a certain moment. In this embodiment, the complex programmable logic device uses the EPM1270T144C5 of the MAXII series produced by Altera, which supports users to update the flash memory configuration when the device is working, supports a variety of dual-end I / O (input / output) interface standards, and has low cost and low power consumption.

[0034] The memory is connected to the CPLD and is used to store all data input by the CPLD. In this embodiment, the memory uses a flash memory with a capacity of 8Kbits, which has enough capacity to store the relevant data results of the CPLD operation.

[0035] The power driving board is connected to the complex programmable logic device and is used to encode the driving signal output by the complex programmable logic device, generate a trigger pulse signal, and output it to the power unit to control the opening and closing of the power device in the power unit.

[0036] The power unit is connected to the power driving board and is used to generate the required compensation current by turning on and off the power device and output it to the power grid. In this embodiment, the power device uses an insulated gate bipolar transistor, which has a fast switching speed and is easy to control. The power unit is an inverter composed of insulated gate bipolar transistors.

[0037] The serial communication device is connected to the complex programmable logic device and is used to complete the data transmission between the complex programmable logic device and the monitoring station. The serial communication device completes the data transmission between the complex programmable logic device and the monitoring station through the RS232 interface, inputs some parameters of the complex programmable logic device into the monitoring station for display, and can also input the control information of the monitoring station into the complex programmable logic device through the serial communication device.

[0038] In this embodiment, each compensation unit is a relatively independent system with the same structure and principle. The controller is connected to the trigger unit, and the trigger unit is connected to multiple compensation units. In this embodiment, the trigger unit is connected to the compensation unit using optical fiber, and there is no electrical connection; the controller calculates the reactive power that needs to be compensated by detecting the voltage and current of the power grid, and determines the group of compensation units that need to be put into or removed according to the reactive power that needs to be compensated. The trigger unit controls the required compensation unit to be put into or removed from the grid for reactive compensation. In this embodiment, the trigger unit is a thyristor trigger unit.

[0039] In this embodiment, the compensation unit is as follows: Figure 2 As shown, the power electronic switch 200 includes a capacitor 100 and a power electronic switch 200 . The power electronic switch 200 includes a thyristor 210 and a diode 220 .

[0040] The thyristor 210 and the diode 220 are connected in reverse parallel, and the thyristor 210 and the diode 220 are electrically connected to the capacitor 100 respectively, so that the capacitor 100 and the power electronic switch 200 are connected. The impact-free switching compensation unit is realized by controlling the conduction and cut-off phases of the thyristor 210. The diode 220 plays a role in charging the capacitor 100, and the forward conduction of the diode 220 provides a charging circuit for the capacitor 100, so no additional pre-charging or pre-throwing circuit is required. In this embodiment, the thyristor can adopt a photoelectric trigger circuit, and the compensation unit can be a modular reactive power compensation unit.

[0041] For example Figure 1 As shown, the trigger unit is used to trigger the thyristor 210. The trigger unit determines the phase of the voltage and current of the capacitor 100. When it is consistent with the voltage and current amplitude and phase of the grid power supply, it controls the conduction or cutoff of the thyristor 210 to enable the compensation unit to be put into operation or removed without causing any impact on the grid.

[0042] In this embodiment, the compensation unit uses a module in which a thyristor 210 and a diode 220 are connected in anti-parallel as the power electronic switch 200. By controlling the conduction time of the thyristor 210 to control the input and removal of the capacitor 100, the capacitor 100 can be switched without impact. The thyristor 210 uses a photoelectric trigger circuit, so it has good anti-interference performance and good isolation effect between strong and weak electricity. The capacitance of the capacitor 100 is 15 kvar to 120 kvar, and the capacitance can be larger. Therefore, the capacitance of the entire reactive power compensation device can be 15 kvar to 600 kvar.

[0043] The advantage of switching capacitors by thyristor switch capacitors (TSC) is that the capacitors 100 are switched by thyristors 210, which can achieve switching without impact. Frequent switching of capacitors 100 does not affect the service life of capacitors 100, and is suitable for decentralized compensation systems with relatively small low-voltage capacity. In addition, the response speed is fast, which can reach 20 milliseconds. In addition, the controller can automatically compensate for the required reactive power according to the real-time situation of the load, so that the compensation effect meets the real-time requirements. In addition, the device can also compensate for unbalanced loads, such as electric welding machines.

[0044] Embodiment 2:

[0045] In this embodiment, a reactive power compensation device, such as Figure 1As shown, it includes a controller, a plurality of compensation units and a trigger unit; the controller is connected to the trigger unit, and the trigger unit is connected to the compensation unit;

[0046] The controller and the trigger unit have the same structure as in Example 1; the compensation unit is as follows: Figure 3 As shown, it specifically includes a capacitor 100, a power electronic switch 200 and a reactor 300, and the power electronic switch 200 includes a thyristor 210 and a diode 220. The thyristor 210 and the diode 220 are respectively connected to the reactor 300, and the reactor 300 is connected to the capacitor 100, so that the reactor 300 is connected in series between the capacitor 100 and the power electronic switch 200.

[0047] In this embodiment, the reactor 300 may be a three-phase iron core reactor. The reactor 300 is connected in series in front of the capacitor 100 to suppress current impact and also to suppress harmonics to a certain extent.

[0048] Embodiment 3:

[0049] In this embodiment, a reactive power compensation device includes a controller, three compensation units and a trigger unit; the controller is connected to the trigger unit, and the trigger unit is connected to the compensation unit;

[0050] The controller and the trigger unit have the same structure as in Example 1; the three compensation units are as follows: Figure 4 As shown, a triangle connection structure is formed, and three compensation units are connected end to end in sequence, and are connected to the three live wires (A, B, C) 12 of the power grid through three wires 11. Each compensation unit includes a capacitor 100, a power electronic switch 200 and a reactor 300. The power electronic switch 200 includes a thyristor 210 and a diode 220. The power electronic switch 200 includes a thyristor 210 and a diode 220, which are respectively connected to the reactor 300, and the reactor 300 is connected to the capacitor 100.

[0051] The role of the diode 220 is to charge the capacitor 100, so no additional pre-charging or pre-investment circuit is required, so it is very different from the existing method. When the current and voltage of the capacitor 100 are completely consistent with the power grid, the thyristor 210 can be turned on according to the control command of the control circuit to put the capacitor 100 into operation. Since the voltage and current of the capacitor 100 are consistent with the power grid at this time, investing the capacitor will not have any impact on the power grid. The moment of cutting off the capacitor 100 is similar to investing. The thyristor is turned off when the voltage and current of the capacitor 100 are consistent with the power grid, so there will be no impact on the power grid. Specifically, when the power electronic switch (knife fuse switch) is closed, the diode 220 is forward-conducted. After closing, there will be a charging current through the diode 220 to charge the capacitor 100. Since the diode 220 and the thyristor 210 are reversely connected in parallel, a reverse voltage will be charged on the capacitor 100, and the voltage amplitude is consistent with the peak value of the voltage of the power grid. When the voltage of the capacitor 100 is consistent with the grid voltage, the thyristor 210 is triggered to conduct, and the capacitor 100 can be put into the grid without causing any impact on the grid. The capacitor 100 is cut off by using the principle that the thyristor 210 current is zero and the voltage is reversed and automatically turned off. At this time, the voltage on the capacitor 100 is still maintained by the diode 220 at the charging voltage, preparing for the next time to be put into use, so no additional pre-investment or pre-charging circuit is required.

[0052] The control of the thyristor 210 adopts a photoelectric control method, that is, the control circuit and the trigger circuit of the thyristor 210 are connected by optical fiber, and the control command is transmitted through an optical signal. Its advantages are fast speed, strong anti-interference ability, and complete isolation of the control power supply and the power supply, making the equipment work safer and more stable.

[0053] Embodiment 4:

[0054] In this embodiment, a reactive power compensation device includes a controller, three compensation units and a trigger unit; the controller is connected to the trigger unit, and the trigger unit is connected to the compensation unit;

[0055] The controller and the trigger unit have the same structure as in Example 1;

[0056] exist Figure 4On the basis of, the three compensation units of the reactive power compensation device of this embodiment form a ring connection structure, each compensation unit 3 includes a capacitor 100, a power electronic switch 200 and a reactor 300, the capacitor 100 and the reactor 300 are connected, and the power electronic switch 200 includes a thyristor 210 and a diode 220 respectively connected to the reactor 300. The three compensation units are connected head to tail in sequence to form a closed loop, and are connected to the three live wires (A, B, C) 12 of the power grid through three wires 11. The diode 220 in each compensation unit 3 is connected to one end of the capacitor 100. The function of the diode is to charge the capacitor. The capacitor 100 in each compensation unit 3 is connected between the power electronic switch 200 and the reactor 300. The capacitor is used to store electrical energy to achieve reactive power compensation. The power electronic switch 200 in each compensation unit 3 includes a thyristor 210 and a diode 220. The thyristor and the diode are respectively connected to the reactor and the capacitor. The reactor 300 in each compensation unit 3 is connected between the power electronic switch and the capacitor. The reactor is used to provide reactive power compensation by adjusting the phase difference between current and voltage. The thyristor 210 in each compensation unit 3 is connected to the reactor. The on and off of the thyristor is controlled by the control circuit to realize the input and removal of the capacitor.

[0057] In this embodiment, the compensation units constituting the ring structure can also form a star topology. The wiring work of the star and ring is similar to that of the triangle, but the controller should be designed according to different circuits. Generally speaking, the number of compensation units in the star structure may be different from that in the ring connection structure. In the star structure, each branch is usually connected to a central node or control unit, rather than being connected to each other as in the ring connection structure.

[0058] Embodiment 5:

[0059] The multiple compensation units in the reactive power compensation device of this embodiment adopt a unitized structure and a modular design, such as Figure 5 As shown, each unit includes a capacitor 100, a reactor 300 and a power electronic switch 200, forming a system; each module structural unit adopts a drawer structure 20, which is convenient for replacement. Figure 5 (right) shows a schematic diagram of the drawer structure of the reactive power compensation device. Its advantage is that the TSC capacity can be easily expanded, for example Figure 5 (Left) shows a schematic diagram of the combined use structure of the reactive power compensation device, which can utilize multiple drawer-type structures 20 to expand multiple module structural units, thereby unifying the specifications of spare parts, reducing the number of spare parts, and reducing maintenance costs.

[0060] The unitized structure in this embodiment means that each unit includes a capacitor 100, a reactor 300 and a power electronic switch 200, that is, a compensation unit; the modular design means Figure 5 (Right) is a box composed of a multi-layer drawer structure, that is, each "drawer" constitutes a module, and then multiple modules constitute a box, which can meet the above requirements.

[0061] The reactive power compensation device of the utility model adopts thyristor switching capacitors, and can realize impact-free switching of capacitors by controlling the moment of thyristor conduction and shutdown, and can frequently switch capacitors without impacting the power grid or damaging the capacitors. At the same time, the use of thyristors as power electronic switches is the basis for realizing fast dynamic regulation of reactive power compensation. When the load of the power grid changes rapidly, the reactive power compensation device can also quickly track and respond, and the response time can reach within 20 milliseconds.

[0062] The reactive power compensation device of the utility model is not only connected in parallel to the power grid, the compensation current can quickly change with the change of the reactive current of the load, automatically compensate the reactive power required by the power grid system, and has low power consumption, high compensation efficiency, large storage capacity and low cost; and the power electronic device is used to switch the capacitor into the power grid for reactive power compensation when the voltage and current of the power grid are consistent with the voltage and current of the capacitor, which has a small impact on the power grid, does not damage the capacitor, is convenient to switch, and has a short response time.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solution described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solution to deviate from the scope defined by the claims of the utility model.

Claims

1. A reactive power compensation device, characterized in that: It includes a controller, a plurality of compensation units and a trigger unit; the controller is connected to the trigger unit, and the trigger unit is connected to the plurality of compensation units; the trigger unit is connected to the compensation unit by optical fiber, and there is no electrical connection; the controller calculates the reactive power to be compensated by detecting the voltage and current of the power grid, and determines the group of compensation units to be put into or removed according to the reactive power to be compensated; The trigger unit controls the compensation unit that needs to be put into or removed from the power grid to perform reactive power compensation on the power grid.

2. A reactive power compensation device according to claim 1, characterized in that: The controller includes: a signal sampling device, an analog-to-digital converter, a complex programmable logic device, a memory, a power driving board and a power unit; The signal sampling device is connected to the power grid and is used to collect current signals and voltage signals of the power grid through a Hall current sensor and a Hall voltage sensor, and output them to an analog-to-digital converter; The analog-to-digital converter is connected to the signal sampling device, and is used to convert the current signal and voltage signal output by the signal sampling device into digital information, and output it to the complex programmable logic device; The complex programmable logic device is connected to the analog-to-digital converter, and is used to analyze the digital information output by the analog-to-digital converter, obtain reactive power information, and output a driving signal to the power driving board according to the reactive power information; The memory is connected to the complex programmable logic device and is used to store all data input by the complex programmable logic device; The power driving board is connected to the complex programmable logic device, and is used to encode the driving signal output by the complex programmable logic device, generate a trigger pulse signal, and output it to the power unit to control the opening and closing of the power device in the power unit; The power unit is connected to the power driving board and is used to generate the required compensation current by turning on and off the power device and output it to the power grid.

3. A reactive power compensation device according to claim 2, characterized in that: The switch device in the power unit is an insulated gate bipolar transistor.

4. A reactive power compensation device according to claim 2, characterized in that: The reactive power compensation device also includes a serial communication device connected to the complex programmable logic device, which is used to complete data transmission between the complex programmable logic device and the monitoring station.

5. A reactive power compensation device according to claim 1, characterized in that: The compensation unit comprises a capacitor and a power electronic switch, and the power electronic switch comprises a thyristor and a diode; the thyristor and the diode are connected in reverse parallel, and the thyristor and the diode are electrically connected to the capacitor respectively.

6. A reactive power compensation device according to claim 1, characterized in that: The reactive power compensation device comprises three compensation units, which form a triangle connection structure. The three compensation units are connected end to end in sequence and are connected to three live wires of a power grid through three conductors.

7. A reactive power compensation device according to claim 1, characterized in that: The reactive power compensation device comprises three compensation units, which form a ring connection structure. The three compensation units are connected end to end in sequence to form a closed loop, and are connected to three live wires of a power grid through three conductors.

8. A reactive power compensation device according to claim 6 or 7, characterized in that: The compensation unit includes a capacitor, a power electronic switch and a reactor, and the power electronic switch includes a thyristor and a diode; The thyristor and the diode are respectively connected to the reactor, and the reactor is connected to the capacitor, so that the reactor is connected in series between the capacitor and the power electronic switch.

9. A reactive power compensation device according to claim 1, characterized in that: The multiple compensation units in the reactive power compensation device adopt a unitized structure and a modular design. Each unit includes a capacitor, a reactor and a power electronic switch, forming a system in itself; each module structural unit adopts a drawer-type structure.

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