Electric energy quality treatment method for distributed photovoltaic transformer area and related device

Abstract

The invention belongs to the technical field of distributed photovoltaic courts, and particularly discloses a distributed photovoltaic court-oriented electric energy quality treatment method and related devices.The distributed photovoltaic court-oriented electric energy quality treatment method comprises the steps that grid-connected voltage of a distributed photovoltaic court is acquired; and adjusting and controlling the reactive power of a photovoltaic inverter and / or a reactive compensation box according to the grid-connected voltage of the distributed photovoltaic transformer area and the upper limit of the safety voltage. The regulation capability of the photovoltaic inverter and the reactive compensation box is comprehensively considered, an energy storage device does not need to be configured in the regulation process, the dependence on the energy storage device is reduced through the coordinated regulation of the photovoltaic inverter and the reactive compensation box, the investment cost and the maintenance cost are reduced, and the regulation efficiency is improved. The electric energy quality problem caused after distributed photovoltaic power generation is connected to the low-voltage distribution network is effectively relieved, and the electric energy quality problem caused after photovoltaic power generation is connected to the low-voltage distribution network can be economically and efficiently solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of distributed photovoltaic areas, and specifically relates to a power quality management method and related devices for distributed photovoltaic areas. Background Art

[0002] With the global attention to the use of renewable energy and technological progress, photovoltaic power generation, as an important part of clean energy, has seen its installed capacity grow rapidly around the world. As the scale of photovoltaic power generation systems connected to low-voltage distribution networks continues to expand, their inherent intermittency and uncertainty have had a significant impact on the power quality of the distribution network, becoming a key technical issue that needs to be urgently addressed in the current power system. In the process of urbanization, electricity demand has become diversified, especially in winter, when urban electricity load has increased significantly due to increased demand for heating. At the same time, photovoltaic power generation is affected by natural factors such as light intensity and weather conditions, and its power generation has obvious volatility and intermittency, making it difficult to fully match the changes in power load. This mismatch between supply and demand has led to random fluctuations in three-phase loads, which in turn has caused a series of power quality problems, such as high and low voltages, heavy loads on distribution transformers, and three-phase imbalance. Especially during peak hours, the sharp fluctuations in single-phase loads have significantly aggravated the three-phase imbalance, which not only causes voltage instability on the user side, but may also cause neutral point offset, aggravate voltage imbalance, and even threaten the safe operation of the power system. In addition, there is often a time mismatch between the peak hours of residential electricity consumption and the strong sunlight hours when photovoltaic power generation is more efficient. This time mismatch further exacerbates the voltage fluctuation problem of the distribution network. When the photovoltaic power generation is large but the load is relatively low during the day, it may cause overvoltage in the distribution network; and when the photovoltaic power generation is not at night but the load increases, it may face the challenge of undervoltage. This voltage fluctuation not only affects the quality and comfort of users' electricity consumption, but also increases the network loss of the power system and reduces the overall energy utilization efficiency.

[0003] With the large-scale integration of distributed photovoltaics into the distribution network, the structure and operating characteristics of the power system have undergone profound changes. The access of distributed photovoltaics weakens the system's short-circuit capacity and voltage stability, making the system more susceptible to various disturbances, thereby increasing the probability of voltage over-limit and other problems. Once the system voltage exceeds the safe range, it may trigger protection actions, causing distributed power sources to be disconnected from the grid or even power outages in the entire power supply area, seriously threatening the stability of power supply. In order to cope with the above problems, the industry has proposed and tried some solutions, such as configuring energy storage devices to smooth the volatility of photovoltaic power generation and alleviate voltage over-limit problems. Although the use of energy storage devices can improve the quality of power to a certain extent, their high investment costs and maintenance costs have become the main factors restricting their widespread application. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a power quality management method and related devices for distributed photovoltaic areas, which can economically and efficiently deal with power quality problems caused by photovoltaic power generation being connected to a low-voltage distribution network.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions: According to a first aspect of the present invention, a method for managing power quality in a distributed photovoltaic area is provided, comprising: Obtain the grid-connected voltage of distributed photovoltaic stations; According to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage, the reactive power of the photovoltaic inverter and / or the reactive power compensation box is adjusted and controlled.

[0006] In a possible implementation of the first aspect, adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive compensation box according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage includes: When the grid-connected voltage of the distributed photovoltaic area is greater than the upper limit of the safety voltage, and the first reactive capacity is greater than the second reactive capacity, the following adjustments are made: First, the grid-connected voltage is adjusted by the reactive power compensation box, and if the voltage is adjusted to below the upper limit of the safety voltage, the adjustment is stopped; Otherwise, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter until it is adjusted to below the upper limit of the safety voltage, and then the adjustment is stopped; The first reactive capacity is the sum of the reactive capacities of the photovoltaic inverter and the reactive compensation box, and the second reactive capacity is the reactive capacity of the distributed photovoltaic area.

[0007] In a possible implementation of the first aspect, the adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive power compensation box according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage further includes: When the grid-connected voltage of the distributed photovoltaic area is greater than the safety voltage upper limit, and the first reactive capacity is not greater than the second reactive capacity, determining whether the first reactive capacity is exhausted; If the first reactive capacity is not exhausted, the reactive power of the reactive compensation box and the photovoltaic inverter are used to jointly adjust the grid-connected voltage; If the first reactive capacity is exhausted, the distributed photovoltaic system is controlled to exit operation until the grid-connected voltage of the distributed photovoltaic area is no greater than the upper safety voltage limit.

[0008] In a possible implementation of the first aspect, adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive compensation box according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage includes: When the grid-connected voltage of the distributed photovoltaic area is not greater than the safety voltage upper limit, the grid-connected voltage is adjusted according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit.

[0009] In a possible implementation of the first aspect, adjusting the grid-connected voltage according to the magnitude between the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit includes: If the grid-connected voltage of the distributed photovoltaic area exceeds the dead zone voltage upper limit, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter.

[0010] In a possible implementation of the first aspect, adjusting the grid-connected voltage according to the magnitude between the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit includes: If the grid-connected voltage of the distributed photovoltaic area does not exceed the dead zone voltage upper limit, no adjustment is performed.

[0011] In a possible implementation manner of the first aspect, the adjusting the grid-connected voltage by using the reactive power of the photovoltaic inverter is specifically: The reactive power of the photovoltaic inverter is controlled by voltage-reactive power droop control.

[0012] According to a second aspect of the present invention, there is provided a power quality management device for a distributed photovoltaic area, comprising: An acquisition module is used to obtain the grid-connected voltage of a distributed photovoltaic station area; The regulating control module is used to regulate and control the reactive power of the photovoltaic inverter and / or reactive compensation box according to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage.

[0013] In a possible implementation of the second aspect, adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive compensation box according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage includes: When the grid-connected voltage of the distributed photovoltaic area is greater than the upper limit of the safety voltage, and the first reactive capacity is greater than the second reactive capacity, the following adjustments are made: First, the grid-connected voltage is adjusted by the reactive power compensation box, and if the voltage is adjusted to below the upper limit of the safety voltage, the adjustment is stopped; Otherwise, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter until it is adjusted to below the upper limit of the safety voltage, and then the adjustment is stopped; The first reactive capacity is the sum of the reactive capacities of the photovoltaic inverter and the reactive compensation box, and the second reactive capacity is the reactive capacity of the distributed photovoltaic area.

[0014] In a possible implementation of the second aspect, the adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive power compensation box according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage further includes: When the grid-connected voltage of the distributed photovoltaic area is greater than the safety voltage upper limit, and the first reactive capacity is not greater than the second reactive capacity, determining whether the first reactive capacity is exhausted; If the first reactive capacity is not exhausted, the reactive power of the reactive compensation box and the photovoltaic inverter are used to jointly adjust the grid-connected voltage; If the first reactive capacity is exhausted, the distributed photovoltaic system is controlled to exit operation until the grid-connected voltage of the distributed photovoltaic area is no greater than the upper safety voltage limit.

[0015] In a possible implementation of the second aspect, adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive compensation box according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage includes: When the grid-connected voltage of the distributed photovoltaic area is not greater than the safety voltage upper limit, the grid-connected voltage is adjusted according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit.

[0016] In a possible implementation of the second aspect, adjusting the grid-connected voltage according to the magnitude between the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit includes: If the grid-connected voltage of the distributed photovoltaic area exceeds the dead zone voltage upper limit, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter.

[0017] In a possible implementation of the second aspect, adjusting the grid-connected voltage according to the magnitude between the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit includes: If the grid-connected voltage of the distributed photovoltaic area does not exceed the dead zone voltage upper limit, no adjustment is performed.

[0018] According to a third aspect of the present invention, there is provided a device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for power quality management for distributed photovoltaic areas when executing the computer program.

[0019] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of a method for power quality management for distributed photovoltaic areas.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides a power quality management method for distributed photovoltaic areas. According to the size of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage, the reactive power of the photovoltaic inverter and / or the reactive compensation box is adjusted and controlled, and the adjustment capabilities of the photovoltaic inverter and the reactive compensation box are comprehensively considered. During the adjustment process, there is no need to configure an energy storage device. Through the coordinated adjustment of the photovoltaic inverter and the reactive compensation box, the dependence on the energy storage device is reduced, the investment cost and maintenance cost are reduced, and the power quality problems caused by the distributed photovoltaic access to the low-voltage distribution network are effectively alleviated, thereby improving the stability of the power system.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the specific implementation modes of the present invention, the drawings required for use in the description of the specific implementation modes will be briefly introduced below. Obviously, the drawings described below are some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a flow chart of a method for managing power quality in a distributed photovoltaic area according to an embodiment of the present invention; Figure 2 Schematic diagram of Q (U) droop control strategy in the embodiment; Figure 3 The present invention is a block diagram of a power quality management device for distributed photovoltaic areas according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] like Figure 1As shown, the embodiment of the present invention provides a power quality management method for distributed photovoltaic areas, which effectively alleviates the power quality problems caused by the access of distributed photovoltaics to the low-voltage distribution network under the premise of reducing the management cost as much as possible. The management method specifically includes the following steps: S1. Obtain the grid-connected voltage of the distributed photovoltaic area.

[0026] Exemplarily, a high-precision voltage sensor is installed at the grid connection point of the distributed photovoltaic area, and the grid connection voltage of the distributed photovoltaic area is monitored in real time by the voltage sensor.

[0027] S2. According to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage, the reactive power of the photovoltaic inverter and / or the reactive power compensation box is adjusted and controlled.

[0028] Specifically, the collected grid-connected voltage data of distributed photovoltaic stations are processed, the difference between the current voltage value and the upper limit of the safe voltage (set according to national standards or grid company regulations) is calculated, and the voltage status is evaluated.

[0029] For example, when it is detected that the grid-connected voltage is close to or exceeds the upper limit of the safety voltage, an attempt is made to reduce the voltage by adjusting the reactive power output of the photovoltaic inverter. Specific strategies may include: Inject an appropriate amount of inductive reactive current into the photovoltaic inverter to consume the excess inductive reactive current in the system, thereby reducing the voltage level; If the PV inverter is currently in the state of generating capacitive reactive power, its capacitive reactive power output will be reduced to slow down the voltage rise trend.

[0030] For example, if the voltage cannot be effectively controlled by adjusting the photovoltaic inverter alone, or a faster voltage response is required, the adjustment strategy of the reactive power compensation box will be started. The specific strategy may include: According to the size and direction of voltage deviation, the capacitor group or reactor group in the reactive power compensation box is automatically switched on or off to quickly compensate or absorb reactive power and achieve precise voltage control; For reactive power compensation boxes with continuous adjustment capabilities, their compensation capacity is gradually adjusted according to the precision of voltage deviation to achieve the optimal voltage control effect.

[0031] The present invention comprehensively considers the adjustment capabilities of the photovoltaic inverter and the reactive power compensation box. There is no need to configure an energy storage device during the adjustment process. Through the coordinated adjustment of the photovoltaic inverter and the reactive power compensation box, the power quality problems caused by the access of distributed photovoltaics to the low-voltage distribution network are effectively alleviated while reducing the management cost, thereby improving the stability of the power system, reducing the dependence on the energy storage device, and reducing the investment cost and maintenance fee.

[0032] It should be understood that the distributed photovoltaic area is already equipped with photovoltaic inverters, reactive power compensation boxes and corresponding voltage monitoring and control systems. The photovoltaic inverter is responsible for converting the direct current generated by the photovoltaic panels into alternating current and feeding it into the power grid, and it also has the ability to regulate reactive power. The reactive power compensation box is used to provide or absorb reactive power in the power grid to stabilize the voltage and improve the power factor of the power grid. The voltage monitoring and control system is responsible for real-time detection of the grid voltage, and makes judgments and adjustments based on the preset safety voltage upper limit.

[0033] In one implementable manner, the reactive power of the photovoltaic inverter and / or the reactive compensation box is adjusted and controlled according to the size of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage, specifically including: when the grid-connected voltage of the distributed photovoltaic area is greater than the upper limit of the safety voltage, and the first reactive capacity is greater than the second reactive capacity, the following adjustments are performed: first, the grid-connected voltage is adjusted by the reactive compensation box, and if it is adjusted to below the upper limit of the safety voltage, the adjustment is stopped; otherwise, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter until it is adjusted to below the upper limit of the safety voltage, and the adjustment is stopped.

[0034] The first reactive capacity is the sum of the reactive capacities of the photovoltaic inverter and the reactive compensation box, and the second reactive capacity is the reactive capacity of the distributed photovoltaic area.

[0035] Specifically, when the grid-connected voltage is monitored to exceed the preset safety voltage upper limit, the total reactive capacity of the current photovoltaic inverter and reactive compensation box (i.e., the first reactive capacity) is calculated first, and the reactive demand of the distributed photovoltaic area (i.e., the second reactive capacity) is evaluated. It should be understood that the first reactive capacity and the second reactive capacity can usually be obtained by querying a preset reactive capacity database.

[0036] If it is determined that the first reactive capacity is greater than the second reactive capacity, that is, the system has sufficient reactive regulation capability to reduce the grid voltage, the regulation function of the reactive compensation box is first started. The specific operation is to adjust the reactive power output or absorption of the reactive compensation box according to the degree of current voltage excess to gradually reduce the grid voltage. During the adjustment process, the change of the grid voltage is continuously monitored. If the grid voltage can be reduced to below the upper limit of the safe voltage after the adjustment of the reactive compensation box, the adjustment is stopped and the current reactive compensation state is maintained. If the grid voltage still fails to drop below the upper limit of the safe voltage after the adjustment of the reactive compensation box, it means that more reactive power is needed to adjust the voltage. At this time, switch to the reactive power adjustment mode of the photovoltaic inverter, and the photovoltaic inverter further reduces the grid voltage by adjusting its reactive power output until it reaches below the upper limit of the safe voltage. When the grid voltage is successfully adjusted to a safe range, the system maintains the current reactive compensation and photovoltaic inverter output state to maintain the stable operation of the power grid. Preferably, the process and results of this adjustment are recorded to provide a reference for subsequent optimization and troubleshooting.

[0037] It should be noted that during the entire adjustment process, the operation safety of the photovoltaic inverter and reactive power compensation box must be ensured to avoid abnormal conditions such as overvoltage and overcurrent. The photovoltaic inverter and reactive power compensation box should also be regularly maintained and inspected to ensure that they are in good working condition.

[0038] Through this implementation, the power quality management for distributed photovoltaic areas can be effectively achieved, especially when the grid-connected voltage exceeds the safety range, by reasonably adjusting the reactive power of the photovoltaic inverter and the reactive power compensation box, the stable operation of the power grid and the improvement of power quality can be ensured.

[0039] In one implementable manner, the reactive power of the photovoltaic inverter and / or the reactive compensation box is adjusted and controlled according to the size of the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage, and also includes: when the grid-connected voltage of the distributed photovoltaic area is greater than the upper limit of the safety voltage, and the first reactive capacity is not greater than the second reactive capacity, it is determined whether the first reactive capacity is exhausted; if the first reactive capacity is not exhausted, the reactive power of the reactive compensation box and the photovoltaic inverter is used to jointly adjust the grid-connected voltage; if the first reactive capacity is exhausted, the distributed photovoltaic is controlled to exit operation until the grid-connected voltage of the distributed photovoltaic area is no greater than the upper limit of the safety voltage.

[0040] That is to say, when the grid-connected voltage of the distributed photovoltaic area exceeds the upper limit of the safety voltage, and the evaluated first reactive capacity (i.e., the sum of the reactive capacity of the photovoltaic inverter and the reactive compensation box) is not greater than the second reactive capacity (i.e., the reactive capacity required by the distributed photovoltaic area), the adequacy of the reactive capacity is first judged. The maximum reactive capacity that the photovoltaic inverter and the reactive compensation box can currently provide is confirmed again, i.e., the first reactive capacity. At the same time, according to the current grid status and the predicted or measured load demand, the reactive capacity required by the distributed photovoltaic area, i.e., the second reactive capacity, is determined. The first reactive capacity is compared with the second reactive capacity to determine whether the system has sufficient reactive regulation capability.

[0041] If the judgment result shows that the first reactive capacity is insufficient but still has some remaining (i.e., not used up), the following joint adjustment strategy will be adopted: using the fast response characteristics of the reactive compensation box, automatically adjust its output or absorbed reactive power according to the degree of voltage excess to quickly reduce the grid voltage; at the same time, the photovoltaic inverter also participates in the adjustment, and gradually adjusts its reactive output according to its reactive power adjustment range and capacity, and works with the reactive compensation box to jointly adjust the grid voltage to a safe range. During the adjustment process, the changes in the grid voltage are continuously monitored to ensure that the adjustment effect meets expectations, and the reactive output of the photovoltaic inverter and reactive compensation box is adjusted in a timely manner to maintain voltage stability.

[0042] If the judgment result shows that the first reactive capacity has been completely exhausted, that is, it is impossible to reduce the grid voltage to a safe range by adjusting the reactive power of the photovoltaic inverter and the reactive compensation box, the following measures will be taken: immediately issue a control command to gradually exit the operation of the distributed photovoltaic system, which can be achieved by reducing the active output of the photovoltaic inverter or completely disconnecting the photovoltaic array from the grid. After the distributed photovoltaic system exits operation, the changes in the grid voltage will be continuously monitored. Once the grid voltage drops below the upper limit of the safe voltage, it will be evaluated whether the distributed photovoltaic system is allowed to reconnect to the grid. If conditions permit, the operation of the distributed photovoltaic system will be gradually restored, and the reactive output of the photovoltaic inverter and the reactive compensation box will be re-evaluated and adjusted to ensure the stable operation of the power grid and the continuous optimization of the power quality.

[0043] This implementation method can adopt flexible and effective adjustment strategies according to the actual situation of reactive capacity when the grid-connected voltage of distributed photovoltaic stations exceeds the safe range, ensuring the stability and power quality of the power grid. At the same time, when the reactive capacity is insufficient, the grid voltage can be prevented from further deteriorating by controlling the exit of distributed photovoltaics, thus ensuring the safe operation of the power system.

[0044] In one implementable manner, the reactive power of the photovoltaic inverter and / or reactive compensation box is adjusted and controlled according to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage, including: when the grid-connected voltage of the distributed photovoltaic area is not greater than the upper limit of the safety voltage, the grid-connected voltage is adjusted according to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the preset dead zone voltage.

[0045] That is to say, when the grid-connected voltage of the distributed photovoltaic area is not greater than the safety voltage upper limit, the system will fine-tune the grid-connected voltage based on the comparison result between the grid-connected voltage and the preset dead zone voltage upper limit to ensure the stability of the power grid and optimize the power quality.

[0046] It should be understood that the preset dead zone voltage upper limit is a voltage value lower than the safety voltage upper limit, which is used to define a safe range in which the grid voltage fluctuation is allowed. When the grid voltage approaches but has not exceeded this upper limit, the system will take preventive measures to adjust to prevent the voltage from further rising above the safety voltage upper limit.

[0047] Specifically, the grid-connected voltage of the distributed photovoltaic area is continuously monitored, and the real-time monitored grid-connected voltage is compared with the preset dead zone voltage upper limit. The comparison results are as follows: Case 1: The grid voltage is lower than the preset dead zone voltage upper limit When the grid-connected voltage is lower than the preset dead zone voltage upper limit, the system considers the current voltage state to be safe and no special adjustment is required. At this time, the system may continue to monitor voltage changes but will not take any active adjustment measures.

[0048] Case 2: The grid-connected voltage approaches or reaches the preset dead zone voltage upper limit When the grid voltage approaches or reaches the preset dead zone voltage upper limit, the preventive adjustment strategy is initiated to prevent the voltage from further increasing. Exemplarily, the reactive power compensation box is used for fine-tuning first, and the grid voltage is stabilized or slightly reduced by adjusting its output or absorbed reactive power. If the reactive power compensation box alone does not adjust well or cannot meet the demand, the reactive power adjustment function of the photovoltaic inverter will be further called, and the two will work together to maintain the grid voltage below the preset dead zone voltage upper limit. During the adjustment process, the changes in the grid voltage are continuously monitored, and the output of the reactive power compensation box and the photovoltaic inverter are adjusted according to the actual situation to keep the voltage within the preset safety range.

[0049] The method of this embodiment can take preventive adjustment measures to ensure the stability of the power grid and optimize the power quality when the grid-connected voltage of the distributed photovoltaic station is within a safe range but close to a preset threshold, which not only helps to prevent the voltage from suddenly rising above the safe voltage upper limit, but also improves the response speed and self-regulation ability of the power grid.

[0050] In one embodiment, the grid-connected voltage is adjusted according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit, including: if the grid-connected voltage of the distributed photovoltaic area exceeds the dead zone voltage upper limit, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter.

[0051] Specifically, when the system monitors that the grid-connected voltage of the distributed photovoltaic area is slightly higher than the preset dead zone voltage upper limit, it means that the grid voltage is approaching an undesirable high value, but has not yet reached an emergency state. At this time, the reactive power regulation function of the photovoltaic inverter is called, and the photovoltaic inverter can flexibly adjust its output or absorbed reactive power to achieve voltage control.

[0052] In one embodiment, the grid-connected voltage is adjusted according to the grid-connected voltage of the distributed photovoltaic area and the preset dead zone voltage upper limit, including: if the grid-connected voltage of the distributed photovoltaic area does not exceed the dead zone voltage upper limit, no adjustment is performed. That is, when the grid-connected voltage of the distributed photovoltaic area does not exceed the preset dead zone voltage upper limit, the strategy adopted by the system is not to perform any active adjustment. This strategy is based on the consideration of grid stability and economy, in order to avoid unnecessary adjustment operations causing additional burden on the grid, it helps to reduce unnecessary equipment operations, extend equipment life, and reduce operating costs.

[0053] In one achievable manner, the grid-connected voltage is regulated by the reactive power of the photovoltaic inverter, specifically: the reactive power of the photovoltaic inverter is controlled by a voltage-reactive power droop control method, thereby achieving the regulation of the grid-connected voltage.

[0054] It should be noted that voltage-reactive droop control is a control strategy based on droop characteristics, which simulates the droop characteristics of generator sets in traditional power systems. In this control strategy, a linear droop relationship is established between the reactive power output of the photovoltaic inverter and the voltage at its grid-connected point. When the grid-connected voltage deviates from the rated value, the reactive power output of the photovoltaic inverter is adjusted to restore the voltage to the desired range. The voltage-reactive droop control method has the advantages of fast response speed and high regulation accuracy, and can effectively stabilize the grid-connected voltage of distributed photovoltaic stations. This control strategy does not require additional communication equipment or a central controller, realizes distributed control, and improves flexibility.

[0055] For example, Q (U) droop control is a very classic voltage control method, and the control curve is as follows Figure 2 shown.

[0056] If the grid-connected voltage of the distributed photovoltaic area is higher than the pre-set target voltage, the photovoltaic inverter absorbs reactive power to delay the rise of the node voltage; conversely, the photovoltaic inverter injects reactive power to delay the decrease of the node voltage; if the grid-connected voltage reaches the upper limit of the network voltage, the photovoltaic inverter absorbs reactive power according to the maximum reactive capacity. Since the power system is always in a dynamic balance process during operation, its voltage will not be fixed all the time, but will fluctuate up and down. When the real-time voltage value is stable in the dead zone (i.e. Figure 2 When the voltage action dead zone is reached, neither active voltage regulation control nor AVC control should be activated. and They are the upper and lower limits of the dead zone voltage, respectively. The setting range of the dead zone voltage will affect the action of the controller. A dead zone voltage that is too wide will have an adverse effect, because the photovoltaic inverter that is close to the substation or distribution transformer in the substation area may not participate in the voltage control at all. Referring to the national standard "GB / T 40289-2021 Technical Requirements for Power Control Systems of Photovoltaic Power Plants", the dead zone voltage range is generally set between ±0.5% and ±2% of the rated voltage.

[0057] In the Q (U) droop control mode, the reactive power target value of the photovoltaic power station is calculated according to the following formula:

[0058] Where: is the reactive power target value of distributed photovoltaics, in per unit value (pu); The grid-connected voltage of distributed photovoltaic is The reactive power corresponding to the time is expressed in per unit value (pu); is the reactive voltage droop control coefficient; is the grid voltage reference value (rated voltage can be taken), the unit is per unit value (pu); It is the measured value of the grid-connected voltage, in per unit (pu). Reactive voltage droop coefficient It should be reasonably set according to the capacity of the distributed photovoltaic reactive compensation box and the actual situation of the local power grid. The general value range is 2~15, and the typical value is 6.

[0059] In another embodiment of the present invention, Figure 3 As shown, a power quality management device for distributed photovoltaic areas is provided, including: An acquisition module is used to obtain the grid-connected voltage of a distributed photovoltaic station area; The regulating control module is used to regulate and control the reactive power of the photovoltaic inverter and / or reactive compensation box according to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage.

[0060] Exemplarily, when the grid-connected voltage of the distributed photovoltaic area is greater than the safety voltage upper limit, and the first reactive capacity is greater than the second reactive capacity, the following adjustments are performed: the grid-connected voltage is first adjusted by the reactive compensation box, and if it is adjusted to below the safety voltage upper limit, the adjustment is stopped; otherwise, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter until it is adjusted to below the safety voltage upper limit, and the adjustment is stopped.

[0061] Exemplarily, when the grid-connected voltage of the distributed photovoltaic area is greater than the upper limit of the safety voltage, and the first reactive capacity is not greater than the second reactive capacity, it is determined whether the first reactive capacity is exhausted; if the first reactive capacity is not exhausted, the reactive power of the reactive compensation box and the photovoltaic inverter are used together to adjust the grid-connected voltage; if the first reactive capacity is exhausted, the distributed photovoltaic is controlled to exit operation until the grid-connected voltage of the distributed photovoltaic area is no greater than the upper limit of the safety voltage.

[0062] Exemplarily, when the grid-connected voltage of the distributed photovoltaic area is not greater than the safety voltage upper limit, the grid-connected voltage is adjusted according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit.

[0063] All relevant contents of each step involved in the aforementioned embodiment of a method for power quality management for distributed photovoltaic areas can be referred to the functional description of the functional modules corresponding to a power quality management device for distributed photovoltaic areas in the embodiment of the present invention, and will not be repeated here. The division of modules in the embodiment of the present invention is schematic, which is only a logical function division. There may be other division methods in actual implementation. In addition, each functional module in each embodiment of the present invention can be integrated into a processor, or it can exist physically separately, or two or more modules can be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software functional modules.

[0064] In another embodiment of the present invention, a computer device is provided, the computer device including a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, which are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of a power quality management method for distributed photovoltaic stations.

[0065] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in a computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the above-mentioned embodiment regarding a method for power quality management for a distributed photovoltaic area.

[0066] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0067] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0068] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0069] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0070] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0071] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for managing power quality in distributed photovoltaic areas, characterized in that: include: Obtain the grid-connected voltage of distributed photovoltaic stations; According to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage, the reactive power of the photovoltaic inverter and / or the reactive power compensation box is adjusted and controlled.

2. According to claim 1, a method for managing power quality in a distributed photovoltaic area is characterized in that: The step of adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive power compensation box according to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage includes: When the grid-connected voltage of the distributed photovoltaic area is greater than the upper limit of the safety voltage, and the first reactive capacity is greater than the second reactive capacity, the following adjustments are made: First, the grid-connected voltage is adjusted by the reactive power compensation box, and if the voltage is adjusted to below the upper limit of the safety voltage, the adjustment is stopped; Otherwise, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter until it is adjusted to below the upper limit of the safety voltage, and then the adjustment is stopped; The first reactive capacity is the sum of the reactive capacities of the photovoltaic inverter and the reactive compensation box, and the second reactive capacity is the reactive capacity of the distributed photovoltaic area.

3. A method for managing power quality in a distributed photovoltaic area according to claim 2, characterized in that: The step of adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive power compensation box according to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage also includes: When the grid-connected voltage of the distributed photovoltaic area is greater than the safety voltage upper limit, and the first reactive capacity is not greater than the second reactive capacity, determining whether the first reactive capacity is exhausted; If the first reactive capacity is not exhausted, the reactive power of the reactive compensation box and the photovoltaic inverter are used to jointly adjust the grid-connected voltage; If the first reactive capacity is exhausted, the distributed photovoltaic system is controlled to exit operation until the grid-connected voltage of the distributed photovoltaic area is no greater than the upper safety voltage limit.

4. The method for managing power quality in a distributed photovoltaic area according to claim 1, characterized in that: The step of adjusting and controlling the reactive power of the photovoltaic inverter and / or the reactive power compensation box according to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage includes: When the grid-connected voltage of the distributed photovoltaic area is not greater than the safety voltage upper limit, the grid-connected voltage is adjusted according to the magnitude of the grid-connected voltage of the distributed photovoltaic area and a preset dead zone voltage upper limit.

5. A method for managing power quality in a distributed photovoltaic area according to claim 4, characterized in that: The step of adjusting the grid-connected voltage according to the grid-connected voltage of the distributed photovoltaic area and the preset dead zone voltage upper limit includes: If the grid-connected voltage of the distributed photovoltaic area exceeds the dead zone voltage upper limit, the grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter.

6. The method for managing power quality in a distributed photovoltaic area according to claim 4, characterized in that: The step of adjusting the grid-connected voltage according to the grid-connected voltage of the distributed photovoltaic area and the preset dead zone voltage upper limit includes: If the grid-connected voltage of the distributed photovoltaic area does not exceed the dead zone voltage upper limit, no adjustment is performed.

7. The method for managing power quality in a distributed photovoltaic area according to claim 5, characterized in that: The grid-connected voltage is adjusted by the reactive power of the photovoltaic inverter, specifically: The reactive power of the photovoltaic inverter is controlled by voltage-reactive power droop control.

8. A power quality management device for distributed photovoltaic areas, characterized in that: include: An acquisition module is used to obtain the grid-connected voltage of a distributed photovoltaic station area; The regulating control module is used to regulate and control the reactive power of the photovoltaic inverter and / or reactive compensation box according to the grid-connected voltage of the distributed photovoltaic area and the upper limit of the safety voltage.

9. A device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of a method for power quality management for distributed photovoltaic areas as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of a method for power quality management for distributed photovoltaic areas as described in any one of claims 1 to 7 are implemented.

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