Reactive compensation device, reactive compensation system and reactive compensation method
By deploying distributed reactive power compensation devices and a central control unit on the low-voltage side of the photovoltaic power station, the problem of reactive power at night in the photovoltaic power station has been solved, and the phase-by-phase smooth regulation of reactive power and the improvement of system stability have been achieved, reducing losses and equipment damage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- THREE GORGES NEW ENERGY LITONG DISTRICT WULIPO PWR GENERATION
- Filing Date
- 2025-12-24
- Publication Date
- 2026-04-21
AI Technical Summary
When centralized photovoltaic power plants are disconnected from the grid at night or operate at low power, the superposition of capacitive charging reactive power and inductive reactive power leads to excess or insufficient reactive power in the system, causing the grid voltage to exceed the limit and increasing grid losses. Existing centralized compensation schemes have problems such as long-distance reactive power flow, large losses, and imprecise regulation.
Distributed reactive power compensation devices are deployed on the low-voltage side of the photovoltaic power generation array, including voltage regulation units, switching units, and compensation units. By adjusting the output voltage and switching compensation modes, phase-by-phase smooth stepless regulation of reactive power is achieved. Combined with the central control unit for coordinated control, the safety and accuracy of the switching process are ensured.
It achieves localized and precise balancing of reactive power in photovoltaic power plants, reduces reactive power flow losses, improves voltage stability and system operation economy, avoids equipment inrush current and arc damage, and extends equipment life and system response speed.
Smart Images
Figure CN121906544A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of new energy power generation technology, and in particular to a reactive power compensation device, a reactive power compensation system, and a reactive power compensation method. Background Technology
[0002] With the large-scale construction of centralized photovoltaic power plants, the reactive power and voltage problems during nighttime grid disconnection or low-power operation have become increasingly prominent. At this time, the capacitive charging reactive power generated by the high-voltage cables in the power plant and the no-load inductive reactive power of the main transformer and box transformer are superimposed, which can easily lead to excess or insufficient reactive power in the system, causing the grid voltage to exceed the limit and increasing grid losses. Summary of the Invention
[0003] To address the aforementioned technical issues, this disclosure provides a reactive power compensation device, a reactive power compensation system, and a reactive power compensation method to achieve smooth and stepless adjustment of reactive power at the subarray level of a photovoltaic power station, thereby improving the system's operational economy and voltage stability.
[0004] In a first aspect, embodiments of this disclosure provide a reactive power compensation device deployed on the low-voltage side bus of a photovoltaic power generation array. The reactive power compensation device includes a voltage regulation unit, a switching unit, and a compensation unit. The input terminal of the voltage regulation unit is connected to the low-voltage side bus. The input terminal of the switching unit is connected to the output terminal of the voltage regulation unit. The input terminal of the compensation unit can be selectively connected to the output terminal of the switching unit.
[0005] The compensation unit includes inductive and capacitive reactive power compensation elements. The switching unit is used to switch the output of the voltage regulation unit to either the inductive or capacitive reactive power compensation element. The voltage regulation unit is used to continuously change the actual voltage applied across the inductive or capacitive reactive power compensation element by adjusting its output voltage.
[0006] In some embodiments, the distributed reactive power compensation device further includes a control unit connected to the voltage regulation unit and the switching unit. The control unit is used to control the voltage output of the voltage regulation unit and the switching operation of the switching unit.
[0007] In some embodiments, the control unit is configured to: first control the voltage regulation unit to reduce the output voltage to zero when performing inductive compensation and capacitive compensation mode switching, and then control the switching unit to switch after the compensation circuit current is zero.
[0008] In some embodiments, the low-voltage side busbar includes a three-phase busbar; the voltage regulating unit, the switching unit, and the compensation unit constitute a three-phase independent structure to achieve independent phase regulation of the low-voltage side busbar.
[0009] In some embodiments, the voltage regulating unit includes three independent single-phase voltage regulators, which are connected one-to-one with the three-phase busbars of the low-voltage side busbar.
[0010] In some embodiments, the compensation unit includes three sets of inductive reactive power compensation elements and capacitive reactive power compensation elements, which are arranged corresponding to the three-phase busbars of the low-voltage side busbar.
[0011] In some embodiments, the switching unit is a dual-throw selector switch.
[0012] Secondly, this disclosure provides a reactive power compensation system, including: a central control unit and a plurality of distributed reactive power compensation devices as provided in any of the foregoing embodiments. The central control unit is communicatively connected to each distributed reactive power compensation device, and the central control unit is used to coordinately control the reactive power output of each distributed reactive power compensation device.
[0013] Thirdly, this disclosure provides a reactive power compensation method, applied to the distributed reactive power compensation device provided in any of the foregoing embodiments. The reactive power compensation method includes: providing a continuously adjustable output voltage through a voltage regulating unit to continuously change the reactive power generated by the compensation unit, thereby achieving smooth stepless compensation; and outputting the output voltage of the voltage regulating unit to an inductive reactive power compensation element or a capacitive reactive power compensation element through a switching unit, thereby achieving switching between inductive compensation mode and capacitive compensation mode.
[0014] In some embodiments, outputting the output voltage of the voltage regulating unit to the inductive reactive power compensation element or the capacitive reactive power compensation element via the switching unit includes: Reduce the output voltage of the voltage regulation unit to zero; Confirm that the current in the compensation circuit is zero; The control switching unit executes the switching operation.
[0015] The reactive power compensation device, reactive power compensation system, and reactive power compensation method provided in this disclosure achieve phase-by-phase smooth stepless adjustment of the reactive power of each subarray by deploying a distributed compensation device including a voltage regulation unit, a switching unit, and a compensation unit on the low-voltage side of the box-type transformer of each photovoltaic power generation array; thereby improving the reactive power support capability and voltage stability level of the photovoltaic power station under special operating conditions such as nighttime. Attached Figure Description
[0016] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.
[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a structural block diagram of the reactive power compensation system provided in the embodiments of this disclosure. Detailed Implementation
[0019] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.
[0020] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.
[0021] The scheme of using centralized static var generators (SVG) or fixed capacitor banks for station-level compensation has problems such as long-distance reactive power flow, large losses, and imprecise regulation, making it difficult to achieve local reactive power balance and rapid dynamic response at the photovoltaic subarray level.
[0022] Based on this, the present disclosure provides a reactive power compensation device, which is deployed on the low-voltage side bus of the photovoltaic power generation array.
[0023] In some embodiments, such as Figure 1 As shown, the reactive power compensation device includes: a voltage regulating unit, a switching unit, and a compensation unit. The input terminal of the voltage regulating unit is connected to the low-voltage side bus. The input terminal of the switching unit is connected to the output terminal of the voltage regulating unit. The input terminal of the compensation unit can be selectively connected to the output terminal of the switching unit.
[0024] The compensation unit includes inductive and capacitive reactive power compensation elements. The switching unit is used to switch the output of the voltage regulation unit to either the inductive or capacitive reactive power compensation element. The voltage regulation unit is used to continuously change the actual voltage applied across the inductive or capacitive reactive power compensation element by adjusting its output voltage.
[0025] This disclosure provides a reactive power compensation device directly deployed on the low-voltage side bus of a photovoltaic power generation array, realizing "distributed" and "localized" reactive power compensation. By selectively connecting the switching unit between inductive and capacitive elements, the inductive or capacitive compensation mode can be flexibly selected.
[0026] By directly connecting the input of the voltage regulating unit to the low-voltage side bus and selectively leading the output to the inductive or capacitive reactive power compensation element via the switching unit, a complete reactive power continuous regulation branch is formed. This structure allows the voltage applied to the selected reactive power element to be continuously changed solely by the output voltage of the voltage regulating unit, thereby achieving smooth and stepless regulation of the reactive power of the subarray. This, in turn, achieves smooth and stepless compensation of the reactive power of the photovoltaic power generation array, fundamentally overcoming the stepped compensation and voltage surge problems caused by traditional group switching. It achieves precise local reactive power balance at the subarray level and significantly reduces reactive power flow losses within the station.
[0027] Specifically, by controlling the output voltage of the voltage regulating unit, the actual voltage applied across the reactor or capacitor is continuously changed. Based on the principle of Q=U² / X, the reactive power absorbed or generated by the reactor or capacitor can be adjusted in a phase-by-phase, smooth, and stepless manner.
[0028] In some embodiments, the distributed reactive power compensation device further includes a voltage regulating unit and a switching unit. The control unit is connected to the switching unit. The control unit is used to control the voltage output of the voltage regulating unit and the switching operation of the switching unit.
[0029] By setting up a control unit connected to the voltage regulating unit and the switching unit, a centralized and automated control interface is provided for the voltage regulation of the voltage regulating unit and the path switching of the switching unit. This enables the device to accept external commands and autonomously execute complete compensation operations, thereby realizing centralized automated control of voltage regulation and switching operations and improving the automation level, response speed and operational reliability of the device.
[0030] In some embodiments, the control unit is configured to: first control the voltage regulation unit to reduce the output voltage to zero when performing inductive compensation and capacitive compensation mode switching, and then control the switching unit to switch after the compensation circuit current is zero.
[0031] By configuring the control unit to reduce the output voltage of the voltage regulating unit to zero and confirm that the current is zero before controlling the switching unit to operate, this control logic ensures that the switching unit operates under zero current conditions. This effectively avoids the problems of inrush current and arcing caused by load operation during the switching process, which can damage the equipment life. From the perspective of operation process mechanism, it avoids the inrush current and arcing caused by load switching, and realizes true zero current and no inrush current switching. This reduces the electrical stress on the switch contacts and reactive power components, and significantly improves the electrical life of the switch components and reactive power components.
[0032] In some embodiments, the low-voltage side busbar includes a three-phase busbar; the voltage regulating unit, the switching unit, and the compensation unit constitute a three-phase independent structure to achieve independent phase regulation of the low-voltage side busbar.
[0033] By configuring the voltage regulating unit, switching unit, and compensation unit into a three-phase independent structure corresponding to the three-phase bus, the problem of the inability to independently compensate for reactive power demand differences caused by load imbalance in the three-phase system is solved. This enables independent detection and adjustment of reactive power for each phase, improves the balance of the three-phase voltage of the system, and avoids equipment overheating or voltage abnormalities caused by overcompensation or undercompensation of a certain phase.
[0034] In some embodiments, the voltage regulating unit includes three independent single-phase voltage regulators, which are connected one-to-one with the three-phase busbars of the low-voltage side busbar.
[0035] By specifically setting the voltage regulation unit as three independent single-phase voltage regulators and connecting them one-to-one with the three-phase busbars, the problem of how to specifically implement the voltage regulation execution component in the three-phase independent structure is solved, providing an independent and continuously adjustable voltage source for each phase, thereby reliably realizing continuous and smooth regulation of phase-by-phase reactive power.
[0036] In some embodiments, the compensation unit includes three sets of inductive reactive power compensation elements and capacitive reactive power compensation elements, which are arranged corresponding to the three-phase busbars of the low-voltage side busbar.
[0037] By setting the inductive and capacitive reactive power compensation elements in the compensation unit independently for each of the three phases, the problem of how to specifically implement the reactive power nature selection component in the three-phase independent structure is solved. This provides each phase with two independent paths: inductive compensation and capacitive compensation, thereby improving the phase-independent compensation function and enabling each phase to independently cope with different reactive power demand characteristics.
[0038] In some embodiments, the switching unit is a dual-throw selector switch.
[0039] By setting a dual-throw selector switch, the switching between two compensation paths (inductive / capacitive) can be achieved in a simple and reliable way. While ensuring functionality, the cost and complexity of the device are reduced, and the economy and practicality are improved.
[0040] In some embodiments, the inductive reactive power compensation element includes a single-phase air-core reactor.
[0041] By using a single-phase air-core reactor, compared to an iron-core reactor, the nonlinear changes in inductance, harmonic amplification, and noise vibration that may occur during voltage regulation due to DC bias or saturation can be avoided. This achieves stability and linearity of the inductance value within a high-precision voltage regulation range, ensuring precise control of the relationship between inductive reactive power and the square of the applied voltage, thereby improving the compensation accuracy and operational reliability of the device.
[0042] In some embodiments, the capacitive reactive power compensation element includes a single-phase self-healing capacitor.
[0043] Ordinary electrolytic capacitors or oil-immersed capacitors suffer from short lifespan and low reliability under frequent switching and continuous voltage regulation conditions. By setting up single-phase self-healing capacitors, which can restore insulation after local dielectric breakdown, high reliability and long lifespan of the capacitors under dynamic operating conditions are achieved, ensuring the continuous and stable operation of the capacitive compensation mode of the device.
[0044] In some embodiments, the reactive power compensation device further includes a subarray local controller, which is connected to a double-throw selector switch and a single-phase voltage regulator. The subarray local controller is used to control the single-phase voltage regulator to adjust the output voltage and to control the double-throw selector switch to perform selection switching.
[0045] In other words, both the dual-throw selector switch and the single-phase voltage regulator are controlled by the subarray local controller. The subarray local controller can receive global commands from the station's central controller via a communication network, thereby enabling or disabling reactive power compensation and precisely adjusting the reactive power output of its own subarray, achieving a balance between subarray-level autonomy and station-level coordination.
[0046] In some embodiments, the subarray controller is hardwired to the inductive reactive power compensation element and the capacitive reactive power compensation element.
[0047] By limiting the signal transmission between the subarray controller and the inductive / capacitive reactive power compensation elements to a hard-wired connection, the problems of signal delay, packet loss, or interference that may exist when using remote communication (such as wireless or network) are solved. This avoids the mismatch between switching actions and voltage regulation status caused by control command transmission delay, thereby fundamentally eliminating the inrush current and arc damage caused by the voltage not returning to zero in time during the switching process, and improving the real-time performance and reliability of the device.
[0048] In summary, the reactive power compensation device provided in some embodiments of this disclosure includes three sets of single-phase voltage regulators, three single-phase air-core reactors, three single-phase self-healing capacitors, and a subarray local controller. Both the dual-throw selector switch and the single-phase voltage regulators are controlled by the subarray local controller.
[0049] The input terminals of the three single-phase voltage regulators are directly connected to the A-phase, B-phase, and C-phase busbars on the low-voltage side of the transformer substation, respectively. The output terminals of the A-phase, B-phase, and C-phase voltage regulators are each connected to a double-throw selector switch. The two output circuits of the double-throw selector switch are connected to a single-phase air-core reactor and a single-phase self-healing capacitor, respectively. This forms a T-shaped reactive power compensation branch: "Low-voltage side of transformer substation → 3 single-phase voltage regulators → double-throw selector switch → reactor / capacitor → return to low-voltage side of transformer substation".
[0050] When switching between capacitive and inductive reactive power compensation modes is required, the local controller of the subarray executes a zero-current switching procedure. That is, the output voltage of the voltage regulator is first reduced to zero, and after confirming that the current in the compensation branch is zero, the double-throw selector switch is controlled to perform the switching operation, which fundamentally eliminates inrush current and arcing, and greatly extends the equipment life.
[0051] This disclosure also provides a reactive power compensation system.
[0052] In some embodiments, the reactive power compensation system includes multiple distributed reactive power compensation devices and a central control unit. The central control unit is communicatively connected to each distributed reactive power compensation device and is used to coordinately control the reactive power output of each distributed reactive power compensation device.
[0053] For example, the reactive power compensation device can be a distributed busbar on the low-voltage side of the box-type transformer deployed in each photovoltaic power generation array.
[0054] For example, the central control unit includes a central controller.
[0055] To achieve optimized control of reactive power and voltage across the entire photovoltaic power plant, a central control unit is set up as the central control system within the plant. This central control unit, communicating with multiple distributed reactive power compensation devices, acts as the "brain" of the entire distributed architecture, realizing a two-layer control architecture of "subarray autonomy + station-level collaboration." Each subarray device achieves rapid and accurate local compensation, while the central control unit optimizes and coordinates based on global information. This ensures both rapid local response and global optimization of reactive power and voltage across the entire plant, effectively avoiding control conflicts and the inability to achieve global optimization that might arise from the independent operation of multiple subarray compensation devices. It achieves centralized coordination and optimized scheduling of reactive power compensation within the plant, giving the system both rapid local response and global collaborative optimization capabilities.
[0056] In some embodiments, each subarray controller in the reactive power compensation device is connected to the central control unit via a fiber optic ring network.
[0057] By limiting the communication architecture between each subarray controller and the central control unit to a fiber optic ring network connection, the problems of low line redundancy, high risk of single-point failure, and signal attenuation and electromagnetic interference affecting communication quality under long-distance transmission, which exist in traditional point-to-point communication or bus communication methods, are solved. This achieves high-speed, low-latency, and high-reliability transmission of data upload and control command issuance, providing a stable and reliable communication guarantee for the central control unit to obtain the reactive power status of each subarray in the whole station in real time and issue global optimization commands. This effectively supports the reliable implementation of the "local autonomy + global collaboration" two-layer control strategy and improves the real-time performance and stability of reactive power collaborative control of the entire power station.
[0058] In some embodiments, the reactive power compensation system further includes a reactive power acquisition device, which is deployed on the outgoing side of the grid connection point and / or on the collection bus of the collector line.
[0059] For example, reactive power acquisition devices are deployed at key nodes of photovoltaic power plants, including but not limited to the outgoing line side of the 110kV grid connection point and the busbar of the 35kV collection line. Through these reactive power acquisition devices, the central control unit can obtain the total amount of reactive power exchanged between the power plant and the grid and the reactive power distribution in various areas of the plant in real time, forming a global view of the reactive power balance of the entire plant.
[0060] Furthermore, based on the aforementioned global information, the central control unit performs advanced calculations and issues instructions such as reactive power setpoints or voltage control targets to the local controllers of each subarray.
[0061] The central control unit defines the coordination rules between subarray autonomy and centralized scheduling. For example, a safe operating dead zone for the subarray bus voltage is set. When the voltage is within the dead zone, the subarray obeys the optimization instructions of the central controller; when the voltage exceeds the limit, the subarray prioritizes local voltage safety control and reports to the central control unit. This coordination rule between subarray autonomy and centralized scheduling effectively avoids control conflicts and ensures system safety.
[0062] This disclosure also provides a reactive power compensation method. The reactive power compensation method can be applied to the aforementioned distributed reactive power compensation device.
[0063] In some embodiments, the reactive power compensation method includes: S1. A continuously adjustable output voltage is provided through the voltage regulation unit to continuously change the reactive power generated by the compensation unit, thereby achieving smooth stepless compensation.
[0064] S2. The output voltage of the voltage regulation unit is output to the inductive reactive power compensation element or the capacitive reactive power compensation element through the switching unit, so as to realize the switching between inductive compensation mode and capacitive compensation mode.
[0065] By executing two core steps—"adjusting the output voltage of the voltage regulating unit to change the reactive power" and "operating the switching unit to select the compensation mode"—a standardized process for achieving smooth stepless compensation and inrush-free switching was clarified, providing a methodological guarantee for the stable and reliable operation of the system.
[0066] In some embodiments, step S2 includes: S21. Reduce the output voltage of the voltage regulating unit to zero; S22. Confirm that the current in the compensation circuit is zero; S23, Control the switching unit to perform the switching operation.
[0067] By specifically executing the process of "reducing voltage to zero, confirming zero current, and then switching" during the switching operation, the problem of ensuring absolute safety and no inrush current during the mode switching process is solved. This provides a standardized switching method that can effectively protect equipment and standardize the operation sequence, thus ensuring the reliability of the system and the lifespan of the equipment from the operational level.
[0068] In summary, this disclosure, taking into account the operational characteristics of centralized ground-mounted photovoltaic power stations after nighttime grid disconnection (such as the dominance of reactive power from cable capacitive charging and significant inductive losses in the main transformer and transformer substation), proposes a distributed reactive power compensation method based on the stepless adjustment of reactors and capacitors deployed in a single array, focusing on dynamic compensation accuracy, economy, and system stability.
[0069] The following describes some embodiments of the reactive power compensation device, reactive power compensation system, and reactive power compensation method of this disclosure in conjunction with practical application scenarios.
[0070] First, modeling is performed based on nighttime reactive power demand.
[0071] The capacitive reactive power of cables is mainly due to the distributed capacitance formed between the conductor and the insulation layer (shielding layer) of the cable, which generates capacitive charging power (i.e., capacitive reactive power) under AC voltage. The calculation formula is as follows:
[0072] Among them, Q line This represents the capacitive reactive power generated by the cable (unit: Var). U represents the operating line voltage of the cable (unit: V); ω represents angular frequency, ω=2πfω=2π (power frequency f=50Hz); C represents the distributed capacitance of the cable (unit: F); Xc represents the capacitive reactance of the cable (unit: Ω). .
[0073] For example, for a 35kV high-voltage cable, the capacitance per unit length of each phase is typically between 0.12 and 0.256 μF / km. Under rated voltage operation, the typical capacitive reactive power generated per kilometer of 35kV cable is approximately 50 to 100 kvar / km.
[0074] The inductive reactive power of the main transformer / substation is mainly due to the inductive reactive power consumed by the transformer during no-load or light-load operation to establish and maintain the magnetic field (excitation flux). This reactive power is mainly generated by the magnetizing inductance of the windings, and its calculation formula is as follows:
[0075] in: Q trans0 This represents the no-load inductive reactive power of the transformer (unit: Var). S0 represents the no-load apparent power (unit: VA); P0 represents the transformer's no-load active power loss (unit: W). I0% represents the percentage of the transformer's no-load current (which can be obtained from the technical parameter table); S N This indicates the rated capacity of the transformer (unit: VA).
[0076] Alternatively, the inductive reactive power of the main transformer / substation can also be simplified and estimated based on the no-load current. The calculation formula is as follows:
[0077] For example, the no-load current percentage (I0%) of a 50MVA two-winding transformer is typically between 0.5% and 1.2%. Therefore, its no-load reactive power consumption is approximately 0.5% × 50000 = 250 kVar to 1.2% × 50000 = 600 kVar.
[0078] Within the subarray, there exists both capacitive reactive power generated by the cable (+Qline, equivalent to reactive "power source") and inductive reactive power consumed by the transformer. Under the condition of Qtrans (equivalent to reactive "load"), the net reactive power demand (or reactive power deficit) of the system is:
[0079] If Q net If the value is greater than 0, it indicates that the system is generally inductive, with a net consumption of inductive reactive power, which needs to be compensated by the addition of capacitor banks to generate capacitive reactive power.
[0080] If Q net If the value is less than 0, it indicates that the system is generally capacitive and generates net capacitive reactive power (i.e., "overcompensation"), requiring the addition of reactor banks to absorb the excess capacitive reactive power.
[0081] The subarray controller calculates the net reactive power Qnet and power factor of the current subarray by collecting voltage and current data in real time, and dynamically switches inductive or capacitive reactive power compensation elements according to preset control logic (such as reactive power deficit threshold and power factor target).
[0082] Through the aforementioned automatic compensation measures, the power factor at the subarray grid connection point is stably controlled above 0.99 (lagging or leading). This not only meets the power grid company's assessment requirements but also effectively reduces reactive power flow in the system network, lowers line losses, and improves voltage stability.
[0083] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0084] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A reactive power compensation device, characterized in that, Deployed on the low-voltage side busbar of the photovoltaic power generation array; the reactive power compensation device includes: A voltage regulating unit, the input of which is connected to the low-voltage side bus; A switching unit, the input of which is connected to the output of the voltage regulating unit; The compensation unit has its input terminal selectively connected to the output terminal of the switching unit; the compensation unit includes an inductive reactive power compensation element and a capacitive reactive power compensation element. The switching unit is used to switch the output of the voltage regulating unit to the inductive reactive power compensation element or the capacitive reactive power compensation element. The voltage regulating unit is used to continuously change the actual voltage applied across the inductive reactive power compensation element or the capacitive reactive power compensation element by adjusting its output voltage.
2. The reactive power compensation device according to claim 1, characterized in that, The distributed reactive power compensation device also includes: The control unit is connected to the voltage regulating unit and the switching unit; The control unit is used to control the voltage output of the voltage regulating unit and the switching operation of the switching unit.
3. The reactive power compensation device according to claim 2, characterized in that, The control unit is configured to: when switching between inductive and capacitive compensation modes, first control the voltage regulation unit to reduce the output voltage to zero, and then control the switching unit to switch after the compensation circuit current is zero.
4. The reactive power compensation device according to claim 1, characterized in that, The low-voltage side busbar includes a three-phase busbar; The voltage regulating unit, the switching unit, and the compensation unit constitute a three-phase independent structure to achieve independent phase regulation of the low-voltage side bus.
5. The reactive power compensation device according to claim 4, characterized in that, The voltage regulating unit includes three independent single-phase voltage regulators, and the three single-phase voltage regulators are connected one-to-one with the three-phase busbars of the low-voltage side busbar.
6. The reactive power compensation device according to claim 4, characterized in that, The compensation unit includes three sets of inductive reactive power compensation elements and capacitive reactive power compensation elements, which are arranged corresponding to the three-phase busbars of the low-voltage side busbar.
7. The reactive power compensation device according to claim 1, characterized in that, The switching unit is a dual-throw selector switch.
8. A reactive power compensation system, characterized in that, include: A plurality of distributed reactive power compensation devices as described in any one of claims 1 to 7, and: The central control unit is communicatively connected to each of the distributed reactive power compensation devices and is used to coordinate the reactive power output of each distributed reactive power compensation device.
9. A reactive power compensation method, characterized in that, Applied to any one of the distributed reactive power compensation devices as described in claims 1 to 7, the reactive power compensation method includes: The voltage regulating unit provides a continuously adjustable output voltage to continuously change the reactive power generated by the compensation unit, thereby achieving smooth stepless compensation. The switching unit outputs the voltage of the voltage regulation unit to the inductive reactive power compensation element or the capacitive reactive power compensation element to achieve switching between inductive compensation mode and capacitive compensation mode.
10. The method according to claim 9, characterized in that, The step of outputting the output voltage of the voltage regulation unit to the inductive reactive power compensation element or the capacitive reactive power compensation element through the switching unit includes: Reduce the output voltage of the voltage regulating unit to zero; Confirm that the current in the compensation circuit is zero; The switching unit is controlled to perform a switching operation.