A voltage and current tracking compensation device

Abstract

The utility model provides a voltage and current tracking compensation device belongs to power electronics technique and analog circuit technical field, through first current calculator, grid side current compensation mechanism and centralized controller closed loop connection, the compensation current of the compensation before current namely load side current and the closed loop connection's grid side current compensation mechanism output is superposed, obtains the current after compensation, through load side voltage sampling mechanism, voltage calculator, centralized controller and load side voltage compensation mechanism are sequentially closed loop connection, the voltage of the compensation before voltage namely grid side voltage and the closed loop connection's load side voltage compensation mechanism output is superposed, obtains the voltage after compensation, the utility model discloses through the voltage compensation mechanism and current compensation mechanism integration unification together, its real -time response speed and open loop are completely same, control optimal steady state compensation effect, has realized high precision, the closed loop control of quick response, has promoted work efficiency.

Description

Technical Field

[0001] This utility model belongs to the fields of power electronics technology and analog circuit technology, and specifically relates to a voltage and current tracking compensation device. Background Technology

[0002] With the rapid development of the information industry and high-tech industries, and the application of computer management and advanced control technologies in traditional industries, the proportion of power loads sensitive to power quality among electricity users is increasing. The modern digital information society places higher demands on power supply reliability and personalized power quality. This means that the information society not only relies on electricity but also requires new and specialized power supplies. This requirement has first attracted attention in economically developed countries.

[0003] In 1988, Dr. Narain G. Hingorani of the Electric Power Research Institute (EPRI) first proposed the new concept of "Custom Power" and its related technologies. In 1996, Hokkaido University and Ibaraki University in Japan jointly proposed the new concept of FRIENDS power supply technology, classifying power quality into three levels. Essentially, this involves applying computer technology, modern control theory, and modern power electronics technology to power distribution systems, creating systems capable of providing high-quality power as well as other power qualities to meet the diverse needs of different users—a concept known as flexible power distribution systems. This reflects the new demands on power quality from the information society and the development of the electricity market, and represents the future direction of next-generation power distribution systems. Therefore, research on the key equipment in flexible power distribution technology—the Unified Power Quality Controller (UPQC)—is of great significance.

[0004] With the development of modern industrial, commercial, and residential electricity consumption, an increasing number of nonlinear loads (such as frequency converters, switching power supplies, electric arc furnaces, LED lighting, and data center server power supplies) and sensitive loads (such as precision manufacturing equipment, medical instruments, data centers, and laboratory equipment) have appeared in the power system. These loads and devices bring serious power quality problems, mainly including voltage quality problems such as voltage sags / boosts, voltage fluctuations, and voltage imbalances on the load side, and current quality problems such as current harmonic distortion, reactive power demand, and load imbalances on the grid side. Utility Model Content

[0005] The purpose of this invention is to provide a voltage and current tracking compensation device to overcome the technical problems of inconsistent and inefficient DVRs and APFs used in existing power systems to improve power quality.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A voltage and current tracking compensation device is installed between a load and a power grid, wherein the power grid is connected to the load via the secondary side of a series transformer; The device includes a grid-side current sampling mechanism, a first current calculator, an output current detector, a grid-side current compensation mechanism, a load-side voltage sampling mechanism, a voltage calculator, a load-side voltage compensation mechanism, and a centralized controller; The input terminal of the grid-side current sampling mechanism is connected to the power grid. The output terminal of the grid-side current sampling mechanism and the output terminal of the output current detector are respectively connected to the input terminal of the first current calculator. The output terminal of the first current calculator is connected to the input terminal of the centralized controller. The input terminal of the output current detector is connected to the current compensation terminal of the grid-side current compensation mechanism. The output terminal of the centralized controller is connected to the input control terminal of the grid-side current compensation mechanism. The current compensation terminal of the grid-side current compensation mechanism is connected to the power grid. The grid-side current compensation mechanism and the load-side voltage compensation mechanism are bidirectionally connected. The input terminal of the load-side voltage sampling mechanism is connected to the load, the output terminal of the load-side voltage sampling mechanism is connected to the input terminal of the voltage calculator, the output terminal of the voltage calculator is connected to the input terminal of the centralized controller, the output terminal of the centralized controller is connected to the input control terminal of the load-side voltage compensation mechanism, and the voltage compensation terminal of the load-side voltage compensation mechanism is connected to the primary side of the series transformer.

[0007] Furthermore, the centralized controller is connected to the input control terminal of the grid-side current compensation mechanism through an output current controller, and the centralized controller is connected to the input control terminal of the load-side voltage compensation mechanism through an output voltage controller.

[0008] Furthermore, the grid-side current compensation mechanism adopts a parallel power unit, and the load-side voltage compensation mechanism adopts a series power unit; The voltage output terminal of the parallel power unit is connected to the voltage input terminal of the series power unit, and the current input terminal of the parallel power unit is connected to the current output terminal of the series power unit.

[0009] Furthermore, both the parallel power unit and the series power unit adopt a three-level modular converter or a two-level power converter.

[0010] Furthermore, the series transformer may be a single-phase coupled transformer, a three-phase coupled transformer, or an isolation transformer.

[0011] Furthermore, a bypass switch is provided on the primary side of the series transformer.

[0012] Furthermore, the bypass switch is a controllable bidirectional thyristor or a combination of a controllable bidirectional thyristor and a contactor.

[0013] Furthermore, the grid-side current sampling mechanism employs a grid current detector.

[0014] Furthermore, the load-side voltage sampling mechanism employs a load voltage detector.

[0015] Furthermore, it also includes a load current detector and a second current calculator. The input terminal of the load current detector is connected to the load, the input terminal of the second current calculator is connected to the output terminal of the load current detector, and the output terminal of the second current calculator is connected to the input terminal of the centralized controller.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a voltage and current tracking compensation device. It connects a first current calculator, a grid-side current compensation mechanism, and a centralized controller in a closed loop. The device superimposes the pre-compensation current (load-side current) with the compensation current output from the grid-side current compensation mechanism to obtain the compensated current. Similarly, it connects a load-side voltage sampling mechanism, a voltage calculator, a centralized controller, and a load-side voltage compensation mechanism in a closed loop. The device superimposes the pre-compensation voltage (grid-side voltage) with the voltage output from the load-side voltage compensation mechanism to obtain the compensated voltage. By integrating the voltage and current compensation mechanisms and utilizing a closed-loop control method, this invention provides pre-compensation commands based on the calculated load voltage and reactive current. Its real-time response speed is identical to that of an open-loop system, optimizing the steady-state compensation effect and achieving high-precision, fast-response closed-loop control, thus improving work efficiency.

[0017] Preferably, a bypass switch is installed between the series power unit and the primary side of the transformer, which can bypass the primary side of the transformer and achieve the effect of removing the system from the power grid. Attached Figure Description

[0018] Figure 1 This is a structural diagram of a voltage and current tracking compensation device according to the present invention; Figure 2 This is a structural diagram of a voltage and current tracking compensation device according to an embodiment of the present invention; Figure 3 This is the voltage drop waveform of a load without voltage and current tracking compensation devices; Figure 4 The output voltage waveform of the voltage and current tracking compensation device; Figure 5 The waveform of the load voltage after compensation by the voltage and current tracking compensation device; Figure 6 This is a waveform diagram of load voltage rise without voltage and current tracking compensation devices; Figure 7Output voltage waveform of the voltage and current tracking compensation device; Figure 8 Waveform of the load voltage after compensation by the voltage and current tracking compensation device.

[0019] In the diagram, 1. Load; 2. Load-side voltage sampling mechanism; 3. Load current detector; 4. Voltage calculator; 5. Second current calculator; 6. Central controller; 601. Output current controller; 602. Output voltage controller; 7. Grid-side current compensation mechanism; 8. Load-side voltage compensation mechanism; 9. Bypass switch; 10. Series transformer; 11. Grid; 12. Grid-side current sampling mechanism; 13. Output current detector; 14. First current calculator. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0021] In one embodiment of this utility model, a voltage and current tracking compensation device is provided, such as... Figure 1 As shown, the device is installed between the power grid 11 and the load 1, and includes a power grid-side current sampling mechanism 12, an output current detector 13, a series transformer 10, a first current calculator 14, a power grid-side current compensation mechanism 7, a load-side voltage sampling mechanism 2, a voltage calculator 4, a load-side voltage compensation mechanism 8, and a centralized controller 6. This invention is divided into two parts: a voltage compensation unit and a current compensation unit. Specifically, the current compensation unit includes a grid-side current sampling mechanism 12, a first current calculator 14, an output current detector 13, a grid-side current compensation mechanism 7, and a centralized controller 6. The input terminal of the grid-side current sampling mechanism 12 is connected to the output terminal of the grid 11 to detect the instantaneous current value of the grid 11. The output terminals of the grid-side current sampling mechanism 12 and the output terminal of the output current detector 13 are respectively connected to the input terminal of the first current calculator 14. The output terminal of the first current calculator 14 is connected to the input terminal of the centralized controller 6. The output terminal of the centralized controller 6 is connected to the input control terminal of the grid-side current compensation mechanism 7. The current compensation terminal of the grid-side current compensation mechanism 7 is connected to both the grid 11 and the input terminal of the output current detector 13. The grid-side current compensation mechanism 7 is bidirectionally connected to the load-side voltage compensation mechanism 8. On the grid 11 side, the output current detector 13, the first current calculator 14, the centralized controller 6, and the grid-side current compensation mechanism 7 are connected in sequence to form a closed-loop connection structure. The current compensation unit includes a load-side voltage sampling mechanism 2, a voltage calculator 4, a load-side voltage compensation mechanism 8, a series transformer 10, and a centralized controller 6. The output terminal of the load 1 is connected to the input terminal of the load-side voltage sampling mechanism 2, the output terminal of the load-side voltage sampling mechanism 2 is connected to the input terminal of the centralized controller 6, the output terminal of the centralized controller 6 is connected to the input control terminal of the load-side voltage compensation mechanism 8, the voltage compensation terminal of the load-side voltage compensation mechanism 8 is connected to the primary side of the series transformer 10, and the secondary side of the series transformer 10 is connected to the load 1. On the load 1 side, the load-side voltage sampling mechanism 2, the voltage calculator 4, the centralized controller 6, the load-side voltage compensation mechanism 8, and the series transformer 10 are connected in sequence to form a closed-loop connection structure.

[0022] Specifically, the grid-side current compensation mechanism 7 adopts a parallel power unit, and the load-side voltage compensation mechanism 8 adopts a series power unit. The voltage output terminal of the parallel power unit is connected to the voltage input terminal of the series power unit, and the current input terminal of the parallel power unit is connected to the current output terminal of the series power unit. The secondary side of the series transformer 10 is set on the DC bus between the grid 11 and the load 1.

[0023] In one optional embodiment, a voltage and current tracking compensation device is disclosed, including a parallel power unit, a series power unit, a bypass switch 9, a series transformer 10, a centralized controller 6, a grid current detector, a first current calculator 14, an output current detector 13, a load-side voltage sampling mechanism 2, and a voltage calculator 4. The parallel power unit is connected to the grid 11 and its main function is to convert AC to DC, stabilize the DC bus voltage, and obtain the current data in the grid 11 through the grid current detector. The required output current is calculated to compensate for the grid current. The series power unit is connected to the parallel power unit through the DC bus. The series power unit draws power from the DC bus, converts the DC voltage to AC voltage output, and obtains the load-side voltage data through the load-side voltage sampling mechanism 2. The required output voltage is calculated using existing methods. The output terminals of the series power unit are respectively connected to the primary side of three single-phase series transformers 10. The secondary side of the single-phase series transformers 10 is connected in series to the three phases A, B, and C of the grid 11 to compensate for the voltage on the load side. The bypass switch 9 is connected to the input of the primary side of the series transformer 10 to bypass the primary side of the series transformer 10, thereby achieving the effect of removing the system from the power grid. Through the technical solution of this utility model, low-loss and high-efficiency compensation can be achieved, the steady-state compensation effect can be controlled to the optimal level, and closed-loop control of voltage and current can be realized.

[0024] The secondary side of the series transformer 10 is connected in series with the power grid 11 and the load 1 respectively. The compensated load-side voltage is the sum of the grid voltage before compensation and the compensated voltage output after closed-loop control. Similarly, the compensated grid-side current is the sum of the load-side current before compensation and the compensated current output after closed-loop control.

[0025] In another embodiment of this utility model, a voltage and current tracking compensation device is provided, such as... Figure 2 As shown, this is used to compensate for the voltage on the load side and the current in the power grid, wherein: The input terminal of the grid current detector is connected to the grid 11, and the output terminal of the grid current detector is connected to the input terminal of the first current calculator 14. The output terminal of the first current calculator 14 is connected to the input terminal of the centralized controller 6. The input terminal of the load current detector 3 is connected to the load 1, and the output terminal of the load current detector 3 is connected to the input terminal of the second current calculator 5. The output terminal of the second current calculator 5 is connected to the input terminal of the centralized controller 6. The input terminal of the output current detector 13 is connected to the grid bus, and the output terminal of the output current detector 13 is connected to the input terminal of the first current calculator 14. The load-side voltage sampling mechanism 2 uses a load voltage detector. The input terminal of the load voltage detector is connected to the load 1, and the output terminal of the load voltage detector is connected to the input terminal of the voltage calculator 4. The output terminal of the voltage calculator 4 is connected to the input terminal of the centralized controller 6. The current compensation terminal of the parallel power unit is connected to the grid 11, and the parallel power unit is bidirectionally connected to the series power unit, such as... Figure 2 As shown, the input control terminal of the parallel power unit is connected to the output current controller 601 in the centralized controller 6; the input control terminal of the series power unit is connected to the output voltage controller 602; the output terminal of the series power unit is connected to the primary side of the series transformer 10; and the secondary side of the series transformer 10 is connected to the power grid 11.

[0026] Optionally, the grid current detector, load current detector 3, and output current detector 13 adopt current transformers or Hall current sensors; the output current controller 601 adopts PID output current control, repetitive current control, or hysteresis current control; the output voltage controller 602 adopts PID output voltage control; the parallel power unit and the series power unit adopt three-level modular converters or two-level modular converters; the bypass switch 9 is a controllable bidirectional thyristor or a combination of a controllable bidirectional thyristor and a contactor; the series transformer 10 adopts a single-phase coupling transformer, a three-phase coupling transformer, or an isolation transformer.

[0027] Ideally, the voltage and current of grid 11 are smooth sine waves with a frequency of 50Hz and an effective value of 220V. like Figure 3 As shown, when the voltage of grid 11 drops or when the load is far from the power supply transformer, due to the impedance and loss of the line, when the active power of load 1 is too large, it will cause the voltage at load 1 to drop and the voltage amplitude to decrease, resulting in a power failure at load 1. When the voltage and current tracking compensation device is running, the instantaneous value of the load-side voltage is detected by the load voltage detector. The voltage calculator 4 outputs a voltage that is in phase and direction with the grid voltage. The centralized controller 6 sends commands to the series power units, and through closed-loop control, such as… Figure 4As shown, since the device is connected in series to the power grid 11, the voltage output by the device in the same direction will be superimposed on the voltage of the power grid 11, which can compensate the voltage on the load side of the power grid to the required target value, such as... Figure 5 As shown; When the voltage of grid 11 rises, or when photovoltaic or electrical energy flows back into grid 11 from load 1, the voltage of load 1 will increase, causing a power outage at load 1. Figure 6 As shown; When the voltage and current tracking compensation device is running, the device detects the instantaneous value of the load-side voltage through the load voltage detector, obtains the output voltage that is in phase but opposite in direction to the voltage of the power grid 11 through the voltage calculator 4, and sends commands to the series power unit module through the central controller 6. Through closed-loop control, such as... Figure 7 As shown, the voltage output in the opposite direction by the device will be subtracted from the voltage of the power grid 11, which can reduce the voltage on the load side of the power grid to the required target value, such as... Figure 8 As shown; When the voltage and current tracking compensation device stops outputting, regardless of whether it is due to an internal equipment fault or external manual shutdown, the bypass switch 9 will automatically close, bypassing the primary side of the series transformer 10. The impedance of the secondary side of the series transformer 10 will become the minimum value, at which point the equipment loss will be the lowest, thus saving power. In addition, a load current detector 3 and a second current calculator 5 are also installed on the load 1 side. The second current calculator 5 is connected to the central controller 6 and is used to determine whether the power on the load 1 side meets the requirements.

[0028] Both series and parallel power units employ vector control strategies. The main functional modules include a PLL (phase-locked loop) for detecting the voltage phase on the grid side, an output controller, and a comparator. The grid synchronization angle θ is obtained using the PLL and voltage detector. Based on θ, the three-phase voltage and current are transformed onto the D / Q axes, with positive-sequence components ID+ and IQ+, and negative-sequence components ID- and IQ-. Vector control ensures that all setpoints (including output voltage, output current, grid voltage positive and negative sequence D / Q axis components, and load current positive and negative sequence D / Q axis components) reach their set values.

[0029] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present utility model should be included within the protection scope of the present utility model.

Claims

1. A voltage and current tracking compensation device, characterized in that, The device is installed between the load (1) and the power grid (11), and the power grid (11) is connected to the load (1) through the secondary side of the series transformer (10). The device includes a grid-side current sampling mechanism (12), a first current calculator (14), an output current detector (13), a grid-side current compensation mechanism (7), a load-side voltage sampling mechanism (2), a voltage calculator (4), a load-side voltage compensation mechanism (8), and a centralized controller (6). The input end of the grid-side current sampling mechanism (12) is connected to the grid (11). The output end of the grid-side current sampling mechanism (12) and the output end of the output current detector (13) are respectively connected to the input end of the first current calculator (14). The output end of the first current calculator (14) is connected to the input end of the centralized controller (6). The input end of the output current detector (13) is connected to the current compensation end of the grid-side current compensation mechanism (7). The output end of the centralized controller (6) is connected to the input control end of the grid-side current compensation mechanism (7). The current compensation end of the grid-side current compensation mechanism (7) is connected to the grid (11). The grid-side current compensation mechanism (7) and the load-side voltage compensation mechanism (8) are bidirectionally connected. The input end of the load-side voltage sampling mechanism (2) is connected to the load (1), the output end of the load-side voltage sampling mechanism (2) is connected to the input end of the voltage calculator (4), the output end of the voltage calculator (4) is connected to the input end of the centralized controller (6), the output end of the centralized controller (6) is connected to the input control end of the load-side voltage compensation mechanism (8), and the voltage compensation end of the load-side voltage compensation mechanism (8) is connected to the primary side of the series transformer (10).

2. The voltage and current tracking compensation device according to claim 1, characterized in that, The centralized controller (6) is connected to the input control terminal of the grid-side current compensation mechanism (7) through the output current controller (601), and the centralized controller (6) is connected to the input control terminal of the load-side voltage compensation mechanism (8) through the output voltage controller (602).

3. A voltage and current tracking compensation device according to claim 1 or 2, characterized in that, The grid-side current compensation mechanism (7) adopts a parallel power unit, and the load-side voltage compensation mechanism (8) adopts a series power unit; The voltage output terminal of the parallel power unit is connected to the voltage input terminal of the series power unit, and the current input terminal of the parallel power unit is connected to the current output terminal of the series power unit.

4. The voltage and current tracking compensation device according to claim 3, characterized in that, Both the parallel power unit and the series power unit adopt a three-level modular converter or a two-level power converter.

5. A voltage and current tracking compensation device according to claim 1, characterized in that, The series transformer (10) can be a single-phase coupling transformer, a three-phase coupling transformer, or an isolation transformer.

6. A voltage and current tracking compensation device according to claim 1, characterized in that, A bypass switch (9) is provided on the primary side of the series transformer (10).

7. A voltage and current tracking compensation device according to claim 6, characterized in that, The bypass switch (9) is a controllable bidirectional thyristor or a combination of a controllable bidirectional thyristor and a contactor.

8. A voltage and current tracking compensation device according to claim 1, characterized in that, The grid-side current sampling mechanism (12) adopts a grid current detector.

9. A voltage and current tracking compensation device according to claim 1, characterized in that, The load-side voltage sampling mechanism (2) uses a load voltage detector.

10. A voltage and current tracking compensation device according to claim 1, characterized in that, It also includes a load current detector (3) and a second current calculator (5), the input of which is connected to the load (1), the input of which is connected to the output of the load current detector (3), and the output of which is connected to the input of the central controller (6).

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