A reactive power regulation method and device based on water-solar hybridization

Abstract

This invention relates to the field of reactive power and voltage regulation technology, specifically providing a reactive power and voltage regulation method and device based on hydro-solar hybrid power generation. The regulation method includes the following steps: Step S1, acquiring real-time photovoltaic output, load, bus voltage, and reactive power reserve; Step S2, calculating real-time reactive power demand; Step S3, allocating reactive power in the order of reactive power reserve – photovoltaic inverter – hydropower unit; Step S4, predicting reactive power demand at a preset time based on historical data and current weather conditions, generating a pre-allocation strategy, and reserving reactive power in advance. This invention predicts reactive power demand after a preset time and formulates a pre-allocation strategy, while simultaneously reserving reactive power in advance. When reactive power and voltage need to be adjusted, the reactive power reserve is activated according to the pre-allocation strategy, thereby quickly adjusting the reactive power and voltage and improving system response.

Description

Technical Field

[0001] This invention relates to the field of reactive power regulation technology, and in particular to a reactive power regulation method and device based on water-solar hybridization. Background Technology

[0002] To build a new power system dominated by new energy sources, vigorously developing renewable energy sources, represented by photovoltaics, is a major trend in the future development of the power grid. However, single photovoltaic power sources suffer from randomness, volatility, and intermittency, failing to meet grid connection requirements. Hydropower units, with their rapid start-up and shutdown capabilities and natural peak-shaving and frequency-regulating abilities, can compensate for the insufficient power quality of photovoltaic power sources. Through hydro-photovoltaic complementarity, the problems of randomness, volatility, and intermittency in photovoltaic power generation can be effectively solved.

[0003] Currently, voltage regulation devices based on water-solar complementarity use real-time feedback regulation to regulate voltage. However, the device response is lagging, resulting in slow voltage regulation response. Therefore, this application proposes a reactive voltage regulation method and device based on water-solar complementarity. Summary of the Invention

[0004] The purpose of this invention is to provide a reactive power regulation method and device based on hydro-solar hybrid power generation, so as to solve the problem of slow response of current reactive power regulation devices in hydro-solar hybrid power plants.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A reactive power voltage regulation method based on water-solar hybridization, the regulation method comprising the following steps:

[0007] Step S1: Obtain real-time photovoltaic output, load, bus voltage, and reactive power reserve;

[0008] Step S2: Calculate real-time reactive power demand;

[0009] Step S3: Distribute reactive power in the order of reactive power reserve - photovoltaic inverter - hydropower unit;

[0010] Step S4: Based on historical data and current weather conditions, predict the reactive power demand for the preset time, generate a pre-allocation strategy, and reserve reactive power in advance.

[0011] The preferred method for calculating real-time reactive power demand is as follows:

[0012] Step S21: Calculate the basic reactive power demand corresponding to the voltage deviation based on formula (1). : Formula (1) where, This refers to the busbar voltage requirement, which is the voltage requirement for the busbars in the power supply network. For real-time voltage, For voltage deviation, where, ; For line impedance; Step S22, calculate the additional reactive power demand for photovoltaic and load fluctuations based on formulas (2) and (3). as well as The additional reactive power demand for photovoltaic fluctuations is calculated based on formula (2). ;Formula (2)

[0013] in, The correlation coefficient between photovoltaic power output and reactive power demand. The change in photovoltaic output is the fluctuation range of real-time photovoltaic output; the additional reactive power demand due to load fluctuation is calculated based on formula (3):

[0014] Formula (3) where, This refers to the change in active power of the load, i.e., the difference between the "current active power of the load" and the "baseline active power of the load"; step S23, then the reactive power demand added by photovoltaic and load fluctuations. for:

[0015] Formula (4). Preferably, Set a fluctuation threshold, only when The additional reactive power demand for photovoltaic fluctuations is only calculated when the value exceeds the fluctuation threshold.

[0016] Preferably, when the reactive power reserve is less than At that time, reactive power voltage can be adjusted by increasing photovoltaic output or hydropower units.

[0017] Preferably, the steps for predicting reactive power demand are as follows: Step S41, predict the basic reactive power demand at time t based on formula (6). :

[0018] Formula (6) in which, To predict the difference between the bus voltage and the required bus voltage at time t in the future; The difference between the predicted photovoltaic output at time t and the current photovoltaic output is obtained through a photovoltaic power prediction model. To predict the difference between the load active power at time t and the load active power at time t, a load prediction model is used. Preferably, , The calculation is performed through the following steps: Step S411, the real-time photovoltaic output at the current time t0 is obtained based on the SCADA system of the photovoltaic array. Step S412: Predict the photovoltaic output at time t based on the trained short-term photovoltaic power prediction model. Step S413: Calculate based on formula (7) :

[0019] ;Formula (7)

[0020] in, To contribute to photovoltaic power at this moment;

[0021] Step S414: Obtain the current time through the load monitoring system of the hydropower unit's central control center. Real-time load active power ;

[0022] Step S415: Predict the active power load at time t using a classification load forecasting model. Step S416: Calculate based on formula (9) :

[0023] ;Formula (9).

[0024] Preferably, in step S413, if the predicted time t is affected by a sudden weather change, then the equation (8) is applied to... Make corrections: ;Formula (8);

[0025] in, For the corrected photovoltaic output, The meteorological correction factor is used. Preferably, the PI error is corrected based on formula (12) to obtain the corrected predicted reactive power demand. : ;Formula (12)

[0026] in, This is the proportionality coefficient. =0.6~1.0; The integral coefficient is... =0.1~0.3; To account for real-time prediction errors, That is, the current moment Actual reactive power demand and forecast The difference between the basic reactive power demand at any given moment.

[0027] Preferably, the pre-allocation strategy includes the following steps: Step S431, ... Split into short-term volatility reserves and long-term stable reserves Step S432: Short-term fluctuation reserves are allocated to SVG and photovoltaic units, with priority given to SVG and the remainder supplemented by photovoltaic units. Long-term stable reserves are allocated to hydropower units.

[0028] This invention also discloses a reactive power voltage regulation device based on water-solar hybridization, the device comprising:

[0029] A reactive power regulation controller is used to implement the above-mentioned reactive power voltage regulation method based on water-solar complementarity.

[0030] Static var generator (SVR) is used to store reactive power.

[0031] Photovoltaic units are used to generate photovoltaic power and store reactive power.

[0032] Hydropower units are used to generate hydroelectric power and store reactive power.

[0033] In summary, the present invention has the following advantages compared with the prior art:

[0034] The reactive power voltage regulation method based on water-solar complementarity disclosed in this invention predicts the reactive power demand after a preset time and formulates a pre-allocation strategy, while reserving reactive power in advance. When reactive power voltage needs to be regulated, the reactive power reserve is activated according to the pre-allocation strategy, thereby quickly regulating reactive power voltage and improving system response. Attached Figure Description

[0035] Figure 1 This is a flowchart of a reactive power voltage regulation method based on water-solar complementary power supply disclosed in an embodiment of the present invention.

[0036] Figure 2 This is a flowchart illustrating the prediction of reactive power demand in a reactive power voltage regulation method based on water-solar complementarity disclosed in an embodiment of the present invention.

[0037] Figure 3 This is a flowchart of the pre-allocation strategy in a reactive power voltage regulation method based on water-solar complementarity disclosed in an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram of a reactive power voltage regulation device based on water-solar complementary technology disclosed in an embodiment of the present invention. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, an embodiment of the present invention provides a reactive power voltage regulation method based on water-solar hybridization, the regulation method comprising the following steps:

[0041] Step S1: Obtain real-time photovoltaic output, load, bus voltage, and reactive power reserve;

[0042] Step S2: Calculate real-time reactive power demand;

[0043] Step S3: Distribute reactive power in the order of reactive power reserve - photovoltaic inverter - hydropower unit;

[0044] Step S4: Based on historical data and current weather conditions, predict the reactive power demand for the preset time, generate a pre-allocation strategy, and reserve reactive power in advance.

[0045] In this embodiment, the reactive voltage regulation is controlled by the reactive voltage regulation controller in the hydro-solar hybrid power station. When the reactive voltage regulation controller is working, it first obtains the real-time photovoltaic output (photovoltaic power generation), load (load power), bus voltage, and reactive power reserve of the photovoltaic power generation unit. Based on the obtained parameters, the reactive power demand is calculated. After the calculation is completed, if reactive power needs to be supplemented, the reactive power is increased in the order of reactive power reserve, photovoltaic inverter, and hydropower unit. Since the reactive power reserve is used first, when the reactive voltage is regulated, the reactive power reserve can respond quickly and regulate the reactive voltage, thereby improving the system response speed.

[0046] When the reactive voltage regulation controller is working, it also predicts the reactive power demand for a preset time based on historical data and current weather conditions, and generates a pre-allocation strategy to reserve reactive power in advance. When it is necessary to adjust the reactive voltage, it adjusts the reactive voltage in a timely manner according to the pre-allocation strategy.

[0047] The reactive power voltage regulation method based on water-solar complementarity disclosed in this invention predicts the reactive power demand after a preset time and formulates a pre-allocation strategy, while reserving reactive power in advance. When reactive power voltage needs to be regulated, the reactive power reserve is activated according to the pre-allocation strategy, thereby quickly regulating reactive power voltage and improving system response.

[0048] Specifically, in this embodiment, in step S1, the current photovoltaic output (photovoltaic power generation) is obtained through the photovoltaic power generation blocking inverter, and the load power of the bus, bus voltage and reactive power reserve are obtained through the power station monitoring system. The reactive power reserve is either SVG (Static Var Generator) or SVC (Static Var Compensator).

[0049] In this embodiment, the real-time reactive power demand calculation method in step S2 is as follows: Step S21, calculate the basic reactive power demand corresponding to the voltage deviation based on formula (1). : Formula (1) where, This refers to the busbar voltage requirement, which is the voltage requirement for the busbars in the power supply network. For real-time voltage, For voltage deviation, where, ; For line impedance, The calculation method is existing technology. For example, in this embodiment, =220kV, , Step S22: Calculate the additional reactive power demand for photovoltaic and load fluctuations based on formulas (2) and (3). as well as :

[0050] The additional reactive power demand for photovoltaic fluctuations is calculated based on formula (2):

[0051] Formula (2) where, This is the correlation coefficient between photovoltaic (PV) output and reactive power demand, measured in MVar / MW. It reflects the reactive power that needs to be supplemented / reduced for every 1MW fluctuation in PV output, and how fluctuations in PV output lead to changes in grid connection voltage. This embodiment quantifies the correlation between "power fluctuations - voltage changes - reactive power demand". ; This refers to the change in photovoltaic (PV) output, specifically the fluctuation range of real-time PV output. PV output is affected by cloud cover and changes in sunlight, resulting in millisecond-level instantaneous fluctuations (such as output suddenly dropping from 8MW to 6MW within 1 second and then immediately rebounding). These instantaneous fluctuations do not require triggering reactive power regulation (to avoid frequent equipment operation). In engineering practice, the "sliding average output over the previous 5 minutes" is usually chosen as the benchmark value. , The total real-time photovoltaic output of the photovoltaic system is obtained by the SCADA system of the photovoltaic system. This is the sliding average of the photovoltaic output over the previous 5 minutes. Preferably, to avoid unnecessary reactive power adjustments, [the following is used]. Set a fluctuation threshold, only when The additional reactive power demand of photovoltaic fluctuations is calculated only when the value exceeds the fluctuation threshold. In this embodiment, the fluctuation threshold is 2% of the rated installed capacity.

[0052] The additional reactive power demand due to load fluctuations is calculated based on formula (3): ;Formula (3)

[0053] in, This represents the change in the active power of the load, specifically the difference between the "current active power of the load" and the "baseline active power of the load." , The active power of the total load on the busbar. The baseline value for the active power of the load is ϕ, which is typically taken as the sliding average value over the previous 5 minutes in engineering practice. ϕ represents the load power factor angle. In this embodiment, A fluctuation threshold is set to prevent the equipment from frequently operating due to minor load fluctuations. The fluctuation threshold is 2% of the average load.

[0054] Step S23: The reactive power demand added by photovoltaic and load fluctuations. for: In step S23 of formula (4), the reactive power allocation is handled by the reactive voltage regulation controller, and the actual regulation amount is... When reactive power reserve is less than When it is necessary to increase the photovoltaic output by controlling the inverter or adjust the reactive voltage by the hydropower unit, the reactive power reserve is used first when adjusting the reactive voltage, then the photovoltaic output is increased, and the remaining part is borne by the hydropower unit. The adjustment amount of the inverter and the hydropower unit is calculated based on formula (5). ;Formula (5)

[0055] Reactive power reserves include reserves for SVG, inverters, and hydropower units.

[0056] In step S4, such as Figure 2 As shown, the steps for predicting reactive power demand are as follows: Step S41, predict the basic reactive power demand at time t based on formula (6). :

[0057] Formula (6) in which, To predict the difference between the bus voltage and the required bus voltage at time t in the future; The difference between the predicted photovoltaic output at time t and the current photovoltaic output is obtained through a photovoltaic power prediction model. The difference between the load active power at the current time and the future load active power at time t is obtained through a load forecasting model. In this embodiment, Calculate using the following steps:

[0058] Step S411: Obtain the real-time photovoltaic output at the current time t0 using the SCADA system (data acquisition and monitoring control system) based on the photovoltaic module. Step S412: Predict the photovoltaic output at time t based on the trained short-term photovoltaic power prediction model. In this embodiment, the short-term photovoltaic power prediction model is a machine learning model, such as the LSTM / random forest model. The short-term photovoltaic power prediction model is trained using historical data, which includes solar radiation intensity, temperature, altitude, photovoltaic array angle, and photovoltaic output. When predicting the photovoltaic output at time t, the predicted solar radiation intensity, temperature, altitude, and photovoltaic array angle at time t are input into the short-term photovoltaic power prediction model. The solar radiation intensity at time t is predicted using meteorological data (such as cloud cover, wind speed, and wind direction, or the predicted solar irradiance intensity at time t can be obtained directly from a meteorological platform). The temperature and altitude at time t are the current temperature and altitude. The photovoltaic array angle at time t is obtained by the SCADA system of the photovoltaic array. Step S413: Calculate based on formula (7) :

[0059] Formula (7) where, To contribute to photovoltaic power at this moment.

[0060] Preferably, in step S413, if the predicted time t is affected by a sudden weather change, then the equation (8) is applied to... Make corrections: ;Formula (8);

[0061] in, For the corrected photovoltaic output, As a weather correction factor, in this embodiment, k=0.2 for showers, k=0.1 for cloudy days, and k=0 for sunny days. Calculations are based on the parameters of the photovoltaic array and its historical performance under various meteorological conditions. In this embodiment, The calculation is performed through the following steps: Step S414, obtain the current time through the load monitoring system of the hydropower unit's central control center. Real-time load active power Step S415: Predict the active power load at time t using a classification load forecasting model. In this embodiment, the classification load prediction model is a machine learning model, such as an LSTM / random forest model. This model is trained using historical data, including historical industrial load data, enterprise production plans, historical residential load data, temperature, and date type. When predicting the load at time t, the predicted enterprise production plan, temperature, and date type for time t are input into the classification load prediction model to obtain the industrial load at time t. and residential load The total load forecast value is Step S416: Calculate based on formula (9) :

[0062] ;Formula (9)

[0063] In this embodiment, The calculation is performed through the following steps: Step S416, predict the bus voltage at time t based on formula (10). ;

[0064] Formula (10) where, The current bus voltage. The voltage sensitivity of photovoltaic output is the voltage change caused by a 1MW change in photovoltaic output. Load active power-voltage sensitivity, the voltage change caused by a 1MW increase in load; in this embodiment... ;

[0065] Step S417: Calculate based on formula (11) : It should be noted that, in this embodiment, to ensure that formula (11) is used, The accuracy requires daily testing with actual voltage. With predicted voltage Comparison, correction of sensitivity and .

[0066] Step S42: Based on formula (12), perform PI error correction to obtain the corrected predicted reactive power demand. : ;Formula (12)

[0067] in, This is the proportionality coefficient. =0.6~1.0; The integral coefficient is... =0.1~0.3; and These are all parameters that are adjusted in real time. First, take the value 0.8, then... If the deviation between the actual reactive power demand at time t and the actual reactive power demand exceeds the first preset value, it will be reduced to 0.6 in the next prediction. If the error continues to exceed the second preset value, it will be increased. ; First, take a value of 0.2. If "integral saturation" occurs (e.g.) If the error is lower than the minimum reactive power capacity of the equipment, the value should be reduced to 0.1; if the accumulated error cannot be eliminated (>1MVar・min), the value should be increased to 0.3. To account for real-time prediction errors, That is, the current moment Actual reactive power demand and forecast The difference between the basic reactive power demand at any given moment.

[0068] In this embodiment, a pre-allocation strategy is formulated based on priority of response speed, capacity constraints, and economy, such as... Figure 3 As shown, in this embodiment, the pre-allocation strategy is formulated according to the following steps:

[0069] Step S431, to Split into short-term volatility reserves and long-term stable reserves In this step, ; = - ;in, Based on empirical values ​​derived from power quality, historical data, equipment regulation capabilities, and safety margins, in this embodiment, =0.2. Step S432: Short-term fluctuation reserves are allocated to SVG and photovoltaic units, with priority given to SVG and the remainder supplemented by photovoltaic units; long-term stable reserves are allocated to hydropower units.

[0070] It should be noted that during allocation, the SVG reserves a certain percentage (e.g., 20%) of reactive power as a safety margin; the reactive power reserve of the photovoltaic module is less than the available capacity of the photovoltaic module, and the reactive power reserve of the photovoltaic module is a certain percentage (e.g., 40%) of the available capacity of the photovoltaic module.

[0071] The long-term stable reserve is less than the reactive power regulation capacity of hydropower units during the dry season.

[0072] When formulating the pre-allocation strategy, it is also necessary to obtain the status of each device. If a device malfunctions, the pre-allocation strategy is adjusted to ensure that the total reserve remains unchanged.

[0073] In this embodiment, the adjustment method further includes the following steps:

[0074] Step S5: Distribute the pre-allocation strategy to each group (SVG, hydropower unit, and photovoltaic unit) and implement the detection equipment response;

[0075] Step S6: Evaluate the pre-allocation strategy and optimize it in the following directions:

[0076] When the response time of voltage regulation exceeds the preset value, increase the SVG reserve ratio;

[0077] When the total number of times the equipment adjusts due to reserves exceeds the preset value, reduce the reserve ratio of photovoltaic inverters and increase the reserve of hydropower units;

[0078] When the voltage qualification rate is less than the preset value, the long-term stability reserve ratio is increased. Example

[0079] As another embodiment of the present invention, such as Figure 4 As shown, this embodiment also discloses a reactive power voltage regulation device based on water-solar complementary power generation, the device 100 comprising:

[0080] A reactive power regulation controller 101 is used to implement the reactive power voltage regulation method based on water-solar complementarity described in Embodiment 1.

[0081] Static var generator 102 is used to store reactive power;

[0082] Photovoltaic unit 103 is used to generate photovoltaic power and store reactive power;

[0083] Hydropower unit 104 is used to generate hydropower output and store reactive power.

[0084] In this embodiment, the reactive power regulation controller is electrically connected to the static var generator, the photovoltaic unit, and the hydropower unit to issue commands to control the operation of the static var generator, the photovoltaic unit, and the hydropower unit.

[0085] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0086] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of this invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for reactive voltage regulation based on water-pumped solar complementary, characterized in that, The adjusting method comprises the following steps: Step S1, acquiring real-time photovoltaic output, load, bus voltage and reactive power reserve; Step S2, calculating real-time reactive power demand; Step S3, distributing reactive power in the order of reactive power reserve-photovoltaic inverter-hydropower unit; Step S4, predicting reactive power demand in a preset time based on historical data and current weather condition, generating pre-distribution strategy and reserving reactive power in advance; Step S21, calculating the basic reactive power demand corresponding to the voltage deviation based on formula (1) : ; Equation (1) wherein is the bus demand voltage, i.e. the voltage requirement for the bus in the power supply network, is the real-time voltage, is the voltage deviation, wherein ; is the line impedance; Step S22, calculate the additional reactive power demand of photovoltaic and load fluctuation based on formula (2) and formula (3) and : The additional reactive power demand of photovoltaic fluctuation is calculated based on formula (2): ; Equation (2) wherein is the photovoltaic power output and reactive power demand correlation factor, is the photovoltaic power output variation, i.e. the fluctuation amplitude of the real-time photovoltaic power output; The additional reactive power demand of load fluctuation is calculated based on formula (3): ; Equation (3) wherein is the change in load active power, i.e. the difference between the "current load active power" and the "reference load active power"; and φ is the load power factor angle. Step S23, then photovoltaic and load fluctuation additional reactive demand is: Official (4).

2. The method according to claim 1, wherein, A fluctuation threshold is set, and only when The additional reactive demand for photovoltaic fluctuation is calculated only when the fluctuation is greater than the fluctuation threshold. 3.The water-light complementary based reactive voltage regulation method of claim 1, wherein, When the reactive reserve is less than the reactive voltage is adjusted by increasing the photovoltaic output or the hydroelectric unit.

4. The method of claim 1, wherein the method is characterized by, The steps of predicting reactive power demand are as follows: Step S41, predict the basic reactive power demand at future t time based on formula (6) : ; Equation (6) wherein, is the difference between the predicted bus voltage at future time t and the demand voltage of the bus at future time t; is the difference between the predicted photovoltaic output at future time t and the current photovoltaic output, obtained by a photovoltaic power prediction model; is the difference between the predicted load active power at future time t and the current load active power, obtained by a load prediction model.

5. The method according to claim 4, wherein, , By the following steps: Step S411, the SCADA system based on the photovoltaic set acquires real-time photovoltaic output at the current time t0 ; Step S412, predicting the photovoltaic output at time t based on the trained short-term photovoltaic power prediction model ; Step S413, calculating based on formula (7) : ; Equation (7) wherein, Ppv(t) is the photovoltaic power at the current time instant; Step S414, obtaining the real-time load active power of the current time through the load monitoring system of the centralized control center of the hydroelectric generating set . ; Step S415, predicting the active power of the load at time t by using the classification load prediction model ; Step S416, calculating based on formula (9) : ; Equation (9).

6. The method according to claim 5, wherein, In step S413, if the predicted t time is changed by a sudden weather, the following formula (8) is corrected: ​ ; Equation (8); wherein, is the corrected photovoltaic power, is the meteorological correction factor.

7. The method of claim 5, wherein the method further comprises: Based on formula (12) to carry out PI error correction, get the modified prediction reactive power demand : ； Formula (12) wherein, is a proportional coefficient, = 0.6~1.0; is an integral coefficient, = 0.1~0.3; is a real-time prediction error, i.e. the difference between the actual reactive power demand at the current time and the predicted reactive power demand at the time . 8.The water-light complementary based reactive voltage regulation method of claim 4, wherein, The pre-distribution strategy comprises the following steps: Step S431, splitting into short-term fluctuation reserves and long-term stable reserves ; Step S432, distributing short-term fluctuation reserve to SVG and photovoltaic group, preferentially using SVG, and the rest being supplemented by photovoltaic group, and distributing long-term stable reserve to hydropower unit.

9. A reactive voltage regulating device based on water-light complementation, characterized in that, The device comprises: A reactive power adjusting controller for realizing the water-light complementary based reactive power voltage adjusting method in any one of claims 1-8; A static reactive power generator for reserving reactive power; A photovoltaic unit for generating photovoltaic output and reserving reactive power; A hydropower unit for generating hydropower output and reserving reactive power.

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