Unified architecture voltage frequency control method and system for sending out network construction energy storage new energy island through DRU

Abstract

The invention discloses a unified architecture voltage frequency control method and system of a DRU-sent network construction energy storage new energy island. The method and system are suitable for an island system comprising a plurality of new energy storage stations and at least one DRU-side energy storage station. The method adopts a uniformly improved droop control strategy and comprises the following steps of: firstly, comparing actual power of a direct current side with a reference value through a constant direct current power loop to generate a total voltage compensation signal; distributing the voltage to each energy storage station through a reactive power integrated controller, and correcting a voltage reference value of a local reactive power-voltage droop ring of the energy storage station; and finally, in combination with a frequency reference value generated by a local active-frequency droop ring, generating a modulation signal of each energy storage converter, thereby realizing constant control of direct current output power and coordinated distribution of system reactive power. The method can adapt to the active-voltage coupling characteristic of the DRU system, the dispatching power is stably sent out when new energy output fluctuates, the capacity requirement for DRU side energy storage is lowered through reactive power distribution, and the economical efficiency and reliability of the system are improved.

Description

Technical Field

[0001] This invention relates to the field of power technology, specifically to a unified architecture voltage and frequency control method and system for transmitting power from a grid-connected energy storage island via a DRU. Background Technology

[0002] High-voltage direct current (HVDC) transmission technology is a key means of achieving long-distance, high-capacity power transmission, especially suitable for grid integration of renewable energy. Among them, HVDC systems based on diode rectifier units (DRUs) have attracted much attention due to their simple structure and good economy. However, DRUs themselves do not have the ability to actively control the AC side voltage and frequency, and their stable operation depends entirely on the AC system. With the increasing penetration rate of renewable energy, the inertia and damping level of the power system are decreasing, posing challenges to the stability of grid frequency and voltage. Grid-based control (GFC) technology is considered a core technology to ensure the stable operation of grids with a high proportion of renewable energy. Therefore, for renewable energy islanded systems transmitted through DRU-HVDC, grid-based equipment (such as wind turbine converters or grid-based energy storage) is needed to construct stable AC voltage and frequency.

[0003] In traditional high-voltage AC power grids, based on the active power exhibited by the high-voltage inductive grid (…), P )-frequency( f ) / Reactive power ( Q )-Voltage( V Due to the coupling characteristics, traditional network control strategies typically employ... P - f and Q - V Droop control is used to coordinate the parallel operation of multiple power sources, achieving efficient voltage and frequency configuration and stable support. However, in DRU-based HVDC systems, due to the active power transmitted by the DRU ( P ) and AC side voltage ( V There is a strong coupling between them, which is different from that of traditional AC power grids. Pf / QV The coupling mechanisms are completely different. Therefore, traditional positive droop control strategies are difficult to apply on the AC side of a DRU-HVDC system. Therefore, for deep-sea wind fields using DRU-HVDC systems, the industry has proposed... P - V / Q - fThe "anti-droop" control strategy, while based on wind power grids, is difficult to directly extend to DRU-HVDC systems with energy storage grids. Firstly, the main power disturbance sources and voltage / frequency construction mechanisms are fundamentally different. In wind power grid-isolated systems, the main power disturbance originates from the grid-connected turbines themselves; however, in energy storage grid-isolated systems, the main power disturbance source comes from the renewable energy turbines operating alongside the grid. Secondly, the system operating objectives are completely different. The primary objective of deep-sea wind farms is to improve wind energy utilization efficiency, meaning the DRU converter station needs to dynamically track the wind turbine output power to achieve real-time power balance and minimize wind curtailment. Conversely, large-scale onshore energy storage stations typically follow grid dispatch instructions, requiring the delivery of constant dispatch power, with the energy storage system responsible for absorbing or compensating for random fluctuations in renewable energy to maintain AC system stability. Finally, the system still operates in an inductive grid environment, and the introduction of the anti-droop control strategy adds additional challenges. PV and Qf The coupling path is complex. This multi-path, high-dimensional coupling often leads to deterioration of system stability, resulting in a worse stability margin than traditional positive droop control systems, and placing higher demands on controller design.

[0004] In addition, the industry has proposed a positive droop voltage frequency construction scheme specifically for DRU-HVDC systems using energy storage networks. This scheme achieves constant DC power output by adding a DC power control loop to the DRU-side energy storage device. However, the constant power regulation function of this scheme relies entirely on the DRU-side energy storage and does not address the reactive power distribution mechanism of the system. In actual operation, as the DC power output increases, the reactive power share borne by the DRU-side energy storage will continue to increase. Since this scheme lacks the ability to dynamically adjust the reactive power distribution of the system, it places extremely high demands on the capacity of the DRU-side energy storage, significantly increasing the overall system cost. Furthermore, if different energy storage sites adopt different control strategies, it will adversely affect the standardized construction and coordinated operation of actual projects.

[0005] Overall, there is currently no systematic research on grid-connected energy storage islands for DRU-based power transmission systems, and there is a lack of voltage and frequency construction strategies that consider reactive power distribution in grid-connected energy storage islands for DRU-based power transmission systems. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a unified architecture voltage and frequency control method and system for sending power from a DRU to a grid-connected energy storage island. This method can adapt to the special PV coupling characteristics of the DRU and the high proportion of new energy penetration in new energy islands, and can achieve the delivery of constant active power according to dispatch instructions when the output of new energy fluctuates.

[0007] This invention is achieved through the following technical solution: A unified architecture voltage and frequency control method for grid-connected energy storage islands via DRUs, wherein the grid-connected energy storage islands include multiple new energy storage stations and at least one DRU energy storage station installed on the AC bus of the DRU; both the new energy storage stations and the DRU energy storage station are controlled using an improved droop control strategy, including: The actual power on the DC side of the energy storage station is obtained and compared with a given DC power reference value to obtain the DC power error. The DC power error is then input to the PI controller of the constant DC power loop to generate a total voltage compensation signal. The total voltage compensation signal is input to the reactive power centralized controller and distributed according to a preset strategy to obtain the voltage compensation amount of the DRU energy storage station and each new energy energy storage station. Each of the energy storage stations corrects the voltage reference value in its local reactive power-voltage droop control loop based on the voltage compensation amount. Each energy storage station generates a modulation signal for its energy storage converter based on the corrected voltage reference value and the frequency reference value generated by its local active power-frequency droop control loop. The converter is controlled according to the modulation signal to achieve constant control of the DC power output from the DRU and distribution control of the reactive power within the DRU output system.

[0008] Preferably, the frequency reference value generated by the local active power-frequency droop control loop is obtained in the following way: The total power difference is obtained by combining the actual frequency of the DRU output system and the rated frequency of the system with constant frequency control. The total power difference is allocated to obtain the active power compensation amount corresponding to each new energy storage station and DRU energy storage station. The frequency reference value in the active power-frequency loop is corrected using the power compensation amount. The final frequency reference value is obtained through the droop control active power-frequency loop.

[0009] Preferably, the method for determining the voltage reference value in the local reactive power-voltage droop control loop and the frequency reference value in the active power-frequency loop is as follows: The three-phase AC voltage and current of the energy storage station are collected and used as input to the three-phase power calculation module to obtain the active and reactive power actually delivered by the DRU energy storage station. The actual active and reactive power of the energy storage station are used as inputs to the droop controller, and are respectively sent to the active power-frequency loop of the droop controller. P - f ) and reactive power-voltage loop ( Q - V ), to obtain the frequency reference value and voltage reference value of the energy storage station.

[0010] Preferably, the generation of modulation signals for the energy storage converters of each energy storage station specifically includes: Based on the corrected voltage and frequency reference values, corresponding d-axis and q-axis voltage reference values ​​are generated in a synchronous rotating coordinate system. The d-axis and q-axis voltage reference values ​​are input into a voltage-current dual closed-loop controller to obtain a modulated wave signal. The modulated wave signal is input into the PWM generator to generate the pulse control signal for the switching device of the energy storage converter.

[0011] Preferably, a constant power control strategy is adopted for the grid-connected inverter of the new energy power plant in the DRU transmission system, which specifically includes: Based on the voltage and current output by the new energy power generation equipment, the maximum power output value under the current operating condition is obtained through the maximum power point tracking algorithm; Using the maximum power output value as the active power reference value, the modulation signal of the grid-connected inverter is generated through the power outer loop and the current inner loop control to achieve the maximum power output.

[0012] Preferably, the power outer loop and current inner loop control specifically refer to: The maximum power output value is compared with the actual active power output of the grid-connected inverter to obtain the input error of the active power control of the grid-connected inverter of the new energy power station. The active power error is input into the PI controller to obtain the d-axis current reference value of the inner current loop; Based on the d-axis and q-axis current reference values, the modulation signal of the grid-connected inverter is generated through current inner loop control; The modulation signal is input to the PWM generator to generate pulse control signals for the inverter's switching devices and control the inverter so that it can deliver the maximum power of the power generation equipment.

[0013] Preferably, the method further includes: employing a constant DC voltage control strategy for the receiving-end converter station of the high-voltage direct current transmission line, specifically including: The voltage deviation is obtained by comparing the capacitor voltage on the DC side of the receiving-end converter station with the DC voltage reference value; The voltage deviation is processed by a PI controller to generate a d-axis current reference value for the inner current loop. Then, the current loop control generates a modulation signal for the receiving-end converter station to maintain DC voltage stability.

[0014] Preferably, the generation of the modulation signal for the receiving-end converter station via current loop control specifically involves: The d-axis current reference value and the preset q-axis current reference value are input into the current inner loop controller; The current inner loop controller generates the AC side voltage reference signal of the receiving-end converter station based on the input current reference value, the feedback AC side current, and the grid voltage phase provided by the phase-locked loop through decoupling control and PI regulation. The AC side voltage reference signal is sent to the PWM modulation unit to generate a pulse control signal to drive the switching devices of the receiving-end converter station.

[0015] A unified architecture voltage and frequency control system for grid-connected energy storage islands via DRUs, wherein the grid-connected energy storage islands include multiple new energy storage stations and at least one DRU energy storage station installed on the AC bus of the DRU, and the voltage and frequency control system includes: The total voltage compensation module is used to obtain the actual power on the DC side of the energy storage station and compare it with the given DC power reference value to obtain the DC power error. The DC power error is then input to the PI controller of the constant DC power loop to generate a total voltage compensation signal. The voltage compensation distribution module is used to input the total voltage compensation signal to the reactive power centralized controller and distribute it according to a preset strategy to obtain the voltage compensation amount of the DRU energy storage station and each new energy energy storage station. A voltage correction module is used for each of the energy storage stations to correct the voltage reference value in its local reactive power-voltage droop control loop according to the voltage compensation amount. The control module is used by each energy storage station to generate modulation signals for its energy storage converters based on the corrected voltage reference value and the frequency reference value generated by its local active power-frequency droop control loop. The module controls the converters according to the modulation signals to achieve constant control of the DC power output from the DRU and distribution control of the reactive power within the DRU output system.

[0016] An electronic device includes a memory and a processor, characterized in that the memory stores a computer program, and when the processor executes the computer program, it implements the unified architecture voltage and frequency control method for grid-connected energy storage new energy islands as described above.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This application proposes a unified architecture voltage and frequency control for renewable energy islands connected via DRU (Dynamic Renewable Energy Unit) grids. Addressing the strong active power-voltage coupling characteristic unique to DRU transmission systems, this approach utilizes an improved droop control architecture. By introducing a unified DC power-voltage compensation mechanism across multiple renewable energy storage stations and DRU-side energy storage stations, constant control of the DC transmission power is achieved. By monitoring the deviation between the actual DC power and the reference value, a PI controller generates a total voltage compensation signal, which is then distributed to each energy storage station according to a strategy via a centralized controller. This dynamically corrects the voltage reference value of each station's local reactive power-voltage droop loop. This method not only fully utilizes the voltage regulation capabilities of all energy storage stations, enabling the system to stably transmit power according to dispatch instructions even when renewable energy output fluctuates, but also achieves a reasonable distribution of reactive power by coordinating the allocation of voltage compensation, reducing the capacity dependence on DRU-side energy storage and improving system economy and operational flexibility.

[0018] This application also proposes a unified architecture voltage and frequency control system for grid-connected energy storage islands via DRU, an electronic device, and a computer storage medium, which possess all the advantages of the aforementioned unified architecture voltage and frequency control method for grid-connected energy storage islands via DRU. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the grid-connected energy storage new energy island system transmitted via DRU-HVDC as studied in this invention; Figure 2 This is a schematic diagram of the topology of the twelve-pulse diode rectifier station studied in this invention; Figure 3 This is a control structure diagram of the grid-connected constant PQ control used in a new energy grid-connected inverter according to the present invention; Figure 4 This is a control structure diagram of the grid-connected constant DC voltage used in the DRU-HVDC receiving-end converter station according to the present invention. Figure 5 This is a control structure diagram of the current loop and voltage loop of the present invention; in, Figure 5 (a) is a current loop control structure. Figure 5 (b) is a voltage loop control structure.

[0021] Figure 6This is a control structure diagram of the improved droop control of the energy storage converter in the energy storage station of the present invention. Figure 7 The waveforms of the DC power output of the DRU and the frequency of the AC system at the sending end of the new energy power station are shown when the power output of the new energy power station changes. Figure 8 This is a waveform diagram of the DC voltage and DC current on the HVDC of the present invention when the output of the new energy power station changes; Figure 9 The waveforms of voltage and current on the AC side of the DRU of this invention are shown when the power output of the new energy power station changes. Figure 10 The waveforms of the active and reactive power generated by the energy storage station of this invention are shown when the output of the new energy power station changes. Figure 11 The waveforms of active and reactive power generated by the new energy power station of this invention are shown. Figure 12 The waveforms of the DC power output of the DRU and the frequency of the AC system at the sending end as the DC power output scheduling command changes are shown in this invention. Figure 13 The waveforms of DC voltage and DC current on the HVDC of this invention change when the dispatch command for DC power output changes. Figure 14 The waveforms of the voltage and current on the AC side of the DRU of this invention change when the dispatch command for DC power output changes. Figure 15 The waveform diagrams show the active and reactive power generated by the energy storage station of this invention as the dispatch command for DC power transmission changes. Figure 16 The waveform diagrams of active and reactive power generated by the new energy power station of the present invention when the dispatch command of DC power transmission changes. Figure 17 The waveforms of the DC power output of the DRU and the frequency of the AC system at the sending end of the present invention when the voltage compensation amount is changed are shown. Figure 18 This is a waveform diagram of the DC voltage and DC current on the HVDC of the present invention when the voltage compensation amount distribution changes; Figure 19 This is a waveform diagram of the voltage and current on the AC side of the DRU of the present invention when the voltage compensation amount distribution changes; Figure 20 This is a waveform diagram of the active and reactive power generated by the energy storage station of the present invention when the voltage compensation amount distribution changes. Figure 21 This is a waveform diagram of the active and reactive power generated by the new energy power station of the present invention when the voltage compensation distribution changes. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. The components of the embodiments of this application described and illustrated herein can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of this application claimed, but merely represents the selected embodiments of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0024] A unified architecture voltage and frequency control method for a grid-forming energy storage new energy island sent out by a DRU. The grid-forming energy storage new energy island includes multiple new energy stations for wind power or photovoltaic power, new energy storage stations supporting each new energy station, and a DRU energy storage station arranged on the AC side bus of the DRU; the voltage and frequency control method includes the following steps: Step 1: Control the new energy storage stations and the DRU energy storage station in the system by using an improved droop control strategy, so that each grid-forming energy storage station can achieve synchronization with other energy storage stations through the active power - frequency ( P - f ) droop link, and at the same time, control the DC power sent out by the DRU by adjusting the port voltage through an improved reactive power loop to achieve the purpose of constant power output of the DRU, and all energy storage stations can participate in the constant power control by controlling the voltage compensation amount of each energy storage station, and reasonably distribute the reactive power in the AC system.

[0025] Since the control methods of the new energy storage stations and the DRU energy storage station are the same, the DRU energy storage station will be taken as an example for illustration below, which specifically includes the following process: S1.1: Collect the three-phase AC voltage and current of the DRU energy storage station, use them as the input of the three-phase power calculation module, and obtain the actual active power and reactive power sent out by the DRU energy storage station; S1.2: Use the actual active power and reactive power of the DRU energy storage station as the input of the droop controller, and send them into the active power - frequency loop ( P - f ) and the reactive power - voltage loop ( Q - V ) of the droop controller respectively to obtain the frequency reference value and voltage reference value of the DRU energy storage station.

[0026] S1.3: Based on the actual frequency and rated frequency of the system, obtain the input error of the constant frequency control loop of the system, use the input error as the input of constant frequency control, and obtain the total power difference that the system needs to adjust. The system is a DRU output system.

[0027] S1.4: The system's active power centralized controller is used to allocate the total power difference, obtaining the active power compensation amount corresponding to each new energy storage station and DRU energy storage station. This power compensation amount is used to correct the power reference value in the active power-frequency loop. The corrected power reference value is then passed through the droop-controlled active power-frequency loop. P - f The final frequency reference value is obtained; S1.5: Based on the actual power on the DC side of the DRU and the power reference value on the DC side, obtain the DC power error of the constant DC power loop input of the DRU energy storage station; S1.6: The DC power error is sent to the PI controller of the constant DC power loop, and the control signal output by the PI controller is sent to the reactive power centralized controller. The voltage compensation amount of each energy storage station (all new energy energy storage stations and DRU energy storage) is obtained through the distribution of the reactive power centralized controller. The voltage compensation amount is used to correct the voltage reference value in the reactive power-voltage loop (QV) to obtain the final voltage reference value. S1.7: Based on the corrected frequency reference value and voltage reference value, obtain the d-axis and q-axis voltage reference values ​​of the current inner loop control circuit of the DRU side energy storage station, and send them into the voltage and current double closed loop to obtain the modulation signal of the energy storage converter of the DRU side energy storage station. S1.8: Input the modulation signal into the PWM generator to generate pulse control signals for the converter switching devices and control the converter, thereby controlling the DC power output from the DRU and the reactive power distribution within the system.

[0028] Step 2: For grid-connected inverters in new energy power plants, a PQ control strategy is adopted to ensure that the grid-connected inverters in new energy power plants can always deliver the maximum power of the power generation equipment (wind turbines or photovoltaic panels) in the new energy power plant under this operating condition.

[0029] S2.1: Use the voltage and current output of the power generation equipment at the new energy station as input to the MPPT algorithm to obtain the maximum output power of the power generation equipment under the current operating conditions; S2.2: Based on the maximum output power and the actual output power of the grid-connected inverter of the new energy power station, obtain the input error of the active power control of the grid-connected inverter of the new energy power station; S2.3: Use the input error of active power control as the input of the PI controller to obtain the reference value of the d-axis component of the current loop of the inner current loop control circuit of the grid-connected inverter of the new energy power station; S2.4: Set the reference value of the current loop q-axis component of the current inner loop control circuit of the grid-connected inverter of the new energy power station to 0, input the reference values ​​of the current loop d-axis and q-axis components into the current loop, and obtain the modulation signal of the grid-connected inverter of the new energy power station through the current loop; S2.5: Input the modulation signal into the PWM generator to generate pulse control signals for the inverter switching devices and control the inverter to achieve AC / DC power balance of the grid-connected inverter, ensuring that the inverter delivers the maximum power to the power generation equipment (wind turbine or photovoltaic panel) under the current operating conditions.

[0030] Step 3: For the receiving-end converter station of HVDC, implement a grid-following control strategy with constant DC voltage to enable the receiving-end converter station to maintain a constant DC voltage, thereby maintaining the stability of HVDC voltage.

[0031] The receiving-end converter station refers to a converter station located at the receiving end of the HVDC line, which adopts a voltage source converter topology and is configured to operate in constant DC voltage control mode to maintain the stability of the HVDC DC voltage and convert DC power into AC power to be sent to the receiving-end power grid.

[0032] S3.1: Determine the input error of constant voltage control based on the DC-side capacitor voltage of the receiving-end converter station and the reference value of the DC-side capacitor voltage; S3.2: Use the voltage control input error as the input to the PI controller to obtain the reference value of the d-axis component of the current loop; S3.3: Set the reference value of the q-axis component of the current loop to 0, input the reference values ​​of the d-axis and q-axis components of the current loop into the current loop, and obtain the modulation signal of the receiving-end converter station through the current loop; S3.4: Input the modulation signal into the PWM generator to generate pulse control signals for the switching devices of the converter station and control the receiving-end converter station to achieve AC / DC power balance of the grid-connected inverter, ensuring constant DC-side capacitor voltage and maintaining HVDC voltage stability.

[0033] Through the above control of the DRU energy storage station, new energy energy storage station, receiving-end converter station and grid-connected inverter of new energy power plant, the voltage and frequency of the grid-connected energy storage new energy island system transmitted by DRU-HVDC are finally realized to achieve stable and reliable construction. The island can transmit power to the outside through DRU to maintain a constant power, and can control the distribution of reactive power by changing the voltage compensation centralized controller.

[0034] Example 1 Taking a 100% renewable energy island via a DRU transmission system as an example, the unified architecture voltage and frequency control method of this application for a grid-connected renewable energy island via a DRU transmission system is applied to the renewable energy island to control the DRU transmission system.

[0035] (1) The structure of this 100% new energy island is as follows: This new energy island architecture is as follows: Figure 1 As shown, the system consists of multiple grid-connected renewable energy power plants and their associated energy storage stations, as well as an additional energy storage station configured on the DRU AC bus for controlling the AC voltage amplitude of the DRU. The total rated power of the renewable energy island in this system is 100MW, with the wind farm having a rated power of 33MW and the two photovoltaic power plants having rated powers of 33MW and 34MW respectively. The wind farm's associated energy storage has a rated power of 5MW, the two photovoltaic power plants' associated energy storage has a rated power of 10MW each, and the energy storage on the DRU AC bus has a rated power of 15MW, totaling 40MW of energy storage capacity, accounting for 40% of the renewable energy power plant's rated power. The wind farm's collection point is connected to the DRU AC bus via a 5.2km overhead line and a 0.3km cable, and the photovoltaic power plant's collection point is connected to the DRU AC bus via a 6.8km overhead line. The DRU's rated DC power is 30MW. The HVDC receiving end uses a voltage source converter (VSC) as the receiving end converter station. The rated DC voltage of the HVDC is... The 20kV receiving-end VSC uses constant DC voltage control to ensure DC voltage stability. After passing through the converter station, the receiving end is connected to the 110kV power grid, ultimately realizing power transmission.

[0036] To illustrate the necessity of using this invention in a new energy islanded system powered by a DRU-HVDC converter, the characteristics of the DRU are explained. Taking a twelve-pulse diode rectifier as an example, its topology is as follows: Figure 2 As shown. Its DC voltage is the envelope of its AC side line voltage, with twelve pulses within one power frequency cycle. Its average DC voltage... U dc It can be represented as: (1) in It is the effective value of the AC side line voltage of the rectifier. The valve current is the current in the flat current segment. This refers to the leakage reactance of the phase-shifting transformer.

[0037] Phase shifting of equation (1) yields the DC current. I dc The expression can be further used to obtain the DC power of the twelve-pulse diode rectifier. It can be expressed as shown in equation (2): (2) From equation (2), we can obtain that when the DC voltage U dc When the value is constant, the active power Pdc of the DRU is related to the AC side voltage amplitude. E Therefore, traditional network construction strategies are not applicable and need to be improved.

[0038] (2) For grid-connected inverters of new energy power plants, a PQ control strategy is adopted to enable grid-connected inverters of new energy power plants to always deliver the maximum power of the power generation equipment (wind turbines or photovoltaic panels) of the new energy power plants under this operating condition.

[0039] In this embodiment of the DRU-HVDC power transmission system, within the grid-connected energy storage renewable energy island, both wind turbines and photovoltaics utilize a constant PQ grid-following control strategy for grid connection control. Since the control method proposed in this invention is used for constructing the sending-end AC grid and is independent of the DC side, the primary side of the wind and solar power plant is simplified to an ideal voltage source, and this simplification does not affect the effectiveness of the control method of this invention. For ease of explanation, [the following is used...] Figure 3 This represents the circuit topology for grid-connected wind, solar, and energy storage systems. For example... Figure 3 As shown, C f It is a filter capacitor. L f It is a filter inductor. L g and R g Indicates the resistance on the mesh side. U abc Indicates the three-phase voltage of the AC power grid. I abc This represents the three-phase current flowing out of the inverter.

[0040] The principle of constant PQ grid-connected control in wind and solar power grid-connected inverters is as follows: Voltage is sampled at the PCC point. U abc and current I abc The active power output of the inverter was then calculated. P and reactive power Q Send in as Figure 3 The constant power grid control shown in the figure. P ref and Q ref These are the active and reactive power reference values ​​of the converter, respectively. The active power reference value is determined in practice by the MPPT algorithm. The input... P and Q The difference between the value and the reference value is used as follows: Id and I q The reference value is input into the current loop, and adjusted by... I d and I q Size to achieve P ref and Q ref track.

[0041] (3) For the receiving-end converter station of HVDC, implement the grid-following control strategy of constant DC voltage so that the receiving-end converter station can maintain a constant DC voltage, thereby maintaining the stability of HVDC voltage.

[0042] The receiving end VSC uses constant DC voltage control, and its control structure is as follows: Figure 5 As shown. The collected data V dc and V dcref The difference is generated by the PI controller. i d A reference value is fed into the current loop, and the DC-side voltage is controlled by adjusting the output power. Figure 3 , Figure 4 The structure of the current and voltage loops involved is as follows: Figure 5 As shown. Figure 5 (a) is a current loop control structure. Figure 5 (b) is a voltage loop control structure.

[0043] (4) An improved droop control strategy is adopted to control the new energy storage stations and DRU storage stations in the system, so that each grid-connected energy storage station can control the active power-frequency ( P - f The drooping link is synchronized with other energy storage stations. Simultaneously, by adjusting the port voltage through an improved reactive power loop, the DC power output of the DRU is controlled to achieve constant power delivery. Furthermore, by controlling the voltage compensation of each energy storage station, all energy storage stations can participate in constant power control, rationally distributing reactive power in the AC system. In this embodiment, within the grid-connected energy storage island of the DRU-HVDC power transmission system, all energy storage stations utilize improved droop control, as shown in the control structure block diagram below. Figure 6 As shown in the figure. k p This is the active power droop coefficient. k q The reactive power droop factor is the coefficient at the first... i The common coupling point PCC of the energy storage converter PCS collects the AC voltage. U iabc CurrentI iabc Its output active power was then calculated. P i and reactive power Q i The input is fed into the droop control loop. To achieve constant power, a DC power-voltage loop is added to the traditional active power-frequency and reactive power-voltage loops. This loop controls the DC power output from the DRU by controlling the voltage amplitude on the AC side of the DRU. Simultaneously, to achieve reasonable distribution of reactive power in the system, compared to the scheme that only uses a Pdc-V loop for energy storage on the DRU side, this invention applies this improved droop control to each energy storage station in the system, and allocates voltage compensation according to the rated power of the energy storage unit through a centralized controller.

[0044] Figure 6 middle, P dc This is the actual DC power. P dcref The DC power output command is given by the dispatch center. The total compensation amount generated after passing through the PI controller in the voltage centralized controller is then distributed inversely proportionally to the rated power of each energy storage facility to obtain the voltage amplitude compensation amount for each energy storage station. i Apply it to the rated voltage u This allows for the simultaneous control of the DRU's output power and the distribution of reactive power within the system.

[0045] In this embodiment, the energy storage network in the 100% renewable energy island does not have a synchronous machine; therefore, the secondary frequency regulation of the renewable energy power station needs to be handled by the network-based energy storage. To ensure that the system frequency tracks the rated frequency without error, this embodiment adds a constant frequency control loop to the above control method, and its control structure is as follows: Figure 6 As shown. This constant frequency control measures the system frequency, calculates the difference between it and the rated frequency, and then uses a PI controller to obtain the reference change value of the energy storage power. P ref Add the change value to the active power reference value. P ref It achieves error-free frequency adjustment.

[0046] The constant power control strategy for grid-connected energy storage and new energy islanding via DRU-HVDC in this embodiment is an improvement on the positive droop control strategy. It simplifies system coupling characteristics and avoids the use of traditional positive droop control. P - f and QV The voltage frequency of the ring-based power grid is adjusted using improved methods. P dc - VThe loop delivers constant power according to scheduling instructions; simultaneously, it can rely on a constant-frequency control loop to ensure error-free frequency operation under different operating conditions. The voltage-frequency construction strategy proposed in this invention can achieve stable frequency operation and track the commanded power delivery under different power output and wind and solar power output fluctuations.

[0047] A simulation model of a new energy islanded grid-connected energy storage system powered by a DRU-HVDC was built in MATLAB / Simulink, and the unified architecture voltage and frequency control method for new energy islanded grid-connected energy storage systems powered by a DRU, as proposed in this invention, was used. To demonstrate that the voltage and frequency construction strategy proposed in this invention can operate stably and reliably under various scenarios, simulations were conducted under two operating conditions: fluctuations in new energy output and changes in scheduling commands. The verification was successful. The allocation can effectively improve the distribution of reactive power in the system. Simulation verification was conducted under the condition of changing the allocation coefficient.

[0048] Table I Simulation Parameters

[0049] The operating conditions for power fluctuations at renewable energy power plants are as follows: at t=3s, the wind farm output suddenly decreases from 0.5 pu to 0.2 pu, and at t=5s, the output of both photovoltaic power plants suddenly increases from 0.4 pu to 0.8 pu, to simulate the actual power fluctuations at renewable energy power plants. The simulation results are as follows. Figures 7-11 The waveform is shown in the diagram.

[0050] like Figure 7 The figure shows the DC power output from the DRU and the system frequency waveforms during power disturbances at the renewable energy power plant. As can be seen from the figure, the system DC power experiences small fluctuations when the renewable energy power plant's output fluctuates, but returns to its rated steady state within 0.2 seconds. The system frequency also fluctuates during these fluctuations, within a range of 0.6 Hz, and gradually returns to 50 Hz within 1.5 seconds due to the constant frequency control loop. Figure 8 The figure shows the DC voltage and current waveforms of the HVDC converter during power disturbances at the renewable energy power station. As can be seen from the figure, when the power output of the renewable energy power station decreases, the DC voltage and current decrease accordingly by a small amount, with the DC voltage change being approximately 0.25%; when the power output of the renewable energy power station increases, the DC voltage and current increase accordingly, with the DC voltage change being approximately 0.5%. The disturbance is very small and can return to steady state within a very short time under the control of the received-end DC voltage, without affecting the normal power transmission of the system. Figure 9The figure shows the three-phase voltage and current waveforms on the AC side of the DRU during power disturbances at the renewable energy power plant. As can be seen from the figure, under the voltage and frequency construction strategy proposed in this invention, the sending-end AC system operates stably with good voltage and current waveform quality. The voltage and current waveforms show no significant changes when the renewable energy power changes, and the system can operate stably under different operating conditions. Figure 10 The figure shows the active and reactive power waveforms of an energy storage system in a renewable energy island at the sending end. As can be seen from the figure, when the renewable energy output decreases, the energy storage system needs to reduce the power it absorbs to provide more active power for HVDC transmission. Figure 11 The figure shows the output waveform of a renewable energy power station in a renewable energy island at the sending end. As can be seen from the figure, the active and reactive power of the renewable energy power station always follow the power command changes.

[0051] The operating conditions for changing dispatch commands are as follows: at t=3s, the dispatch command changes from 30MW to 40MW, and at t=5s, the dispatch command changes from 40MW to 20MW, to simulate the actual situation of dispatch command changes. The simulation results are as follows. Figures 12-16 The waveform is shown in the diagram. like Figure 12 The figure shows the DC power output from the DRU and the system frequency waveforms when the dispatch command changes. As can be seen from the figure, when the dispatch command changes, the system DC power strictly follows the change in dispatch command under the action of the constant power loop, enabling precise adjustment of the DRU's output power. When the dispatch command changes, the system frequency fluctuates to some extent, within a range of 0.9Hz, and gradually returns to 50Hz within 2 seconds due to the action of the constant frequency control loop. Figure 13 The figure shows the DC voltage and current waveforms of HVDC when the dispatch command changes. As can be seen from the figure, the DC voltage increases slightly when the dispatch command increases. This is because the power transmitted from the sending end increases under the influence of the dispatch command, but the response from the receiving end is slower. Conversely, the voltage increases when the dispatch command decreases. The trend of DC current change is basically consistent with the DC power transmitted, increasing with the increase of the dispatch command and decreasing with the decrease of the dispatch command. Figure 14 The figure shows the three-phase voltage and current waveforms on the AC side of the DRU when the dispatch command changes. As can be seen from the figure, under the voltage-frequency construction strategy proposed in this invention, the sending-end AC system operates stably with good voltage and current waveform quality. The voltage and current waveforms do not change significantly when the dispatch command changes, and the system can operate stably under different operating conditions. When the dispatch command increases, both the sending-end AC voltage and current show a slight increase in amplitude, which is consistent with the theoretical analysis showing a strong coupling between the AC voltage amplitude and the DC power output from the DRU. Figure 15 The figure shows the active and reactive power waveforms of the energy storage system in the renewable energy island at the sending end when dispatch commands change. As can be seen from the figure, when dispatch commands increase, the energy storage system needs to reduce the power it absorbs to provide more active power for HVDC transmission, and vice versa. Figure 16 The figure shows the power output waveform of a renewable energy power station in a renewable energy island at the sending end when the dispatch command changes. As can be seen from the figure, since its given power command does not change, its output active power always remains constant at the rated level.

[0052] To prove the change The allocation can effectively improve the distribution of reactive power. Simulations were conducted under altered operating conditions. The simulation took place between t=0 and 3s. The energy is evenly distributed to each energy storage station, and changes at t=3s. The allocation coefficient is 5:1:1:1, with the voltage compensation for energy storage on the DRU side accounting for a larger value. Simulation results are as follows: Figures 17-21 The waveform is shown in the diagram.

[0053] like Figure 17 The figure shows the DC power output from the DRU and the system frequency waveforms when the voltage compensation allocation method changes. As can be seen from the figure, when the voltage compensation allocation method changes, the system DC power experiences a small change but quickly catches up with the scheduling command again. Simultaneously, the system frequency also fluctuates slightly, with an amplitude of 1.4Hz, and quickly returns to steady state within 0.1s under the action of the constant frequency loop. Figure 18 The diagram shows the DC voltage and current waveforms of HVDC when the voltage compensation distribution method changes. When the voltage compensation distribution method changes, both the DC voltage and current experience short-term fluctuations but quickly return to a steady state. Figure 19 The figure shows the three-phase voltage and current waveforms on the AC side of the DRU when the voltage compensation distribution method changes. As can be seen from the figure, under the voltage frequency construction strategy proposed in this invention, the sending-end AC system operates stably with good voltage and current waveform quality. The voltage and current waveforms do not change significantly when the voltage compensation distribution method changes, and the system can operate stably under different operating conditions. Figure 20 The figure shows the active and reactive power waveforms of the energy storage system in the sending-end renewable energy island when the voltage compensation distribution method changes. As can be seen from the figure, the active power of the energy storage device does not change when the voltage compensation distribution method changes, but when… The reactive power changed significantly when the change occurred, therefore, by changing... The allocation of reactive power can effectively change the distribution of reactive power in the system, thereby providing more freedom in selecting the capacity of energy storage devices and reducing system construction costs. For example... Figure 21 The figure shows the output waveform of a renewable energy power station in a renewable energy island at the sending end when the voltage compensation distribution method changes. As can be seen from the figure, since its given power command remains unchanged, its output active and reactive power always remain at their rated values. The above simulation waveforms illustrate that under different... Under all operating conditions, the system can operate stably and reliably, and The change can effectively alter the distribution of reactive power in the system, through the modification of... The allocation algorithm can rationally allocate the reactive power of the system based on various factors such as the capacity of the energy storage equipment, so that all energy storage stations can participate in constant power control, reduce the capacity requirements of DRU-side energy storage, and reduce construction costs.

[0054] Correspondingly, this application also provides a unified architecture voltage and frequency control system for grid-connected energy storage islands, wherein the grid-connected energy storage islands include multiple new energy storage stations and at least one DRU energy storage station installed on the AC bus of the DRU. The voltage and frequency control system includes: The total voltage compensation module is used to obtain the actual power on the DC side of the energy storage station and compare it with the given DC power reference value to obtain the DC power error. The DC power error is then input to the PI controller of the constant DC power loop to generate a total voltage compensation signal. The voltage compensation distribution module is used to input the total voltage compensation signal to the reactive power centralized controller and distribute it according to a preset strategy to obtain the voltage compensation amount of the DRU energy storage station and each new energy energy storage station. A voltage correction module is used for each of the energy storage stations to correct the voltage reference value in its local reactive power-voltage droop control loop according to the voltage compensation amount. The control module is used by each energy storage station to generate modulation signals for its energy storage converters based on the corrected voltage reference value and the frequency reference value generated by its local active power-frequency droop control loop. The module controls the converters according to the modulation signals to achieve constant control of the DC power output from the DRU and distribution control of the reactive power within the DRU output system.

[0055] It should be noted that, in the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated into another device, or some features may be ignored or not executed. The modules described as separate components may or may not be physically separated. The components shown as modules may be one or more physical units, that is, they may be located in one place or distributed in multiple different places. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment according to actual needs.

[0056] Furthermore, in the various embodiments of the present invention, the modules can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The integrated unit described above can be implemented in hardware or as a software functional unit.

[0057] An electronic device provided in this application includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the unified architecture voltage and frequency control method for sending out grid-connected energy storage new energy islands via DRU as described in any of the above embodiments.

[0058] Another electronic device provided in this application embodiment may further include: an input port connected to a processor for transmitting multimodal data collected by an external acquisition device to the processor; a display unit connected to the processor for displaying the processor's processing results to the outside world; and a communication module connected to the processor for enabling communication between the electronic device and the outside world. The display unit may be a display panel, a laser scanning display, etc.; the communication method adopted by the communication module includes, but is not limited to, Mobile High Definition Link (HML), Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), and wireless connection (including Wi-Fi, Bluetooth, Bluetooth Low Energy, and IEEE 802.11s-based communication technology).

[0059] This application provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the steps of the unified architecture voltage and frequency control method for sending out grid-connected energy storage new energy islands via DRU as described in any of the above embodiments.

[0060] For descriptions of relevant parts of the unified architecture voltage and frequency control system, electronic equipment, and computer-readable storage medium for grid-connected energy storage islands via DRU provided in this application's embodiments, please refer to the detailed description of the corresponding parts in the unified architecture voltage and frequency control method for grid-connected energy storage islands via DRU provided in this application's embodiments; they will not be repeated here. Furthermore, parts of the technical solutions provided in this application that are consistent with the implementation principles of corresponding technical solutions in the prior art have not been described in detail to avoid excessive elaboration.

[0061] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A unified architecture voltage and frequency control method for grid-connected energy storage islands via DRU, characterized in that, The grid-connected energy storage new energy island includes multiple new energy storage stations and at least one DRU energy storage station installed on the AC side bus of the DRU. Both the new energy storage station and the DRU energy storage station adopt an improved droop control strategy for control, including: The actual power on the DC side of the energy storage station is obtained and compared with a given DC power reference value to obtain the DC power error. The DC power error is then input to the PI controller of the constant DC power loop to generate a total voltage compensation signal. The total voltage compensation signal is input to the reactive power centralized controller and distributed according to a preset strategy to obtain the voltage compensation amount of the DRU energy storage station and each new energy energy storage station. Each of the energy storage stations corrects the voltage reference value in its local reactive power-voltage droop control loop based on the voltage compensation amount. Each energy storage station generates a modulation signal for its energy storage converter based on the corrected voltage reference value and the frequency reference value generated by its local active power-frequency droop control loop. The converter is controlled according to the modulation signal to achieve constant control of the DC power output from the DRU and distribution control of the reactive power within the DRU output system.

2. The unified architecture voltage and frequency control method for grid-connected energy storage new energy islands via DRU as described in claim 1, characterized in that, The frequency reference value generated by the local active power-frequency droop control loop is obtained in the following way: The total power difference is obtained by combining the actual frequency of the DRU output system and the rated frequency of the system with constant frequency control. The total power difference is allocated to obtain the active power compensation amount corresponding to each new energy storage station and DRU energy storage station. The frequency reference value in the active power-frequency loop is corrected using the power compensation amount. The final frequency reference value is obtained through the droop control active power-frequency loop.

3. The unified architecture voltage and frequency control method for grid-connected energy storage new energy islands via DRU as described in claim 2, characterized in that, The methods for determining the voltage reference value in the local reactive power-voltage droop control loop and the frequency reference value in the active power-frequency loop are as follows: The three-phase AC voltage and current of the energy storage station are collected and used as input to the three-phase power calculation module to obtain the active and reactive power actually delivered by the DRU energy storage station. The actual active and reactive power of the energy storage station are used as inputs to the droop controller, and are respectively sent to the active power-frequency loop of the droop controller. P - f ) and reactive power-voltage loop ( Q - V ), to obtain the frequency reference value and voltage reference value of the energy storage station.

4. The unified architecture voltage and frequency control method for grid-connected energy storage new energy islands via DRU as described in claim 1, characterized in that, The specific steps of generating the modulation signal for the energy storage converter of each energy storage station include: Based on the corrected voltage and frequency reference values, corresponding d-axis and q-axis voltage reference values ​​are generated in a synchronous rotating coordinate system. The d-axis and q-axis voltage reference values ​​are input into a voltage-current dual closed-loop controller to obtain a modulated wave signal. The modulated wave signal is input into the PWM generator to generate the pulse control signal for the switching device of the energy storage converter.

5. The unified architecture voltage and frequency control method for grid-connected energy storage new energy islands via DRU as described in claim 1, characterized in that, A constant power control strategy is adopted for the grid-connected inverters of new energy power plants in the DRU transmission system, which specifically includes: Based on the voltage and current output by the new energy power generation equipment, the maximum power output value under the current operating condition is obtained through the maximum power point tracking algorithm; Using the maximum power output value as the active power reference value, the modulation signal of the grid-connected inverter is generated through the power outer loop and the current inner loop control to achieve the maximum power output.

6. The unified architecture voltage and frequency control method for grid-connected energy storage new energy islands via DRU as described in claim 5, characterized in that, The power outer loop and current inner loop control are specifically as follows: The maximum power output value is compared with the actual active power output of the grid-connected inverter to obtain the input error of the active power control of the grid-connected inverter of the new energy power station. The active power error is input into the PI controller to obtain the d-axis current reference value of the inner current loop; Based on the d-axis and q-axis current reference values, the modulation signal of the grid-connected inverter is generated through current inner loop control; The modulation signal is input to the PWM generator to generate pulse control signals for the inverter's switching devices and control the inverter so that it can deliver the maximum power of the power generation equipment.

7. The unified architecture voltage and frequency control method for grid-connected energy storage new energy islands via DRU as described in claim 1, characterized in that, The method further includes: employing a constant DC voltage control strategy for the receiving-end converter station of the high-voltage direct current transmission line, specifically including: The voltage deviation is obtained by comparing the capacitor voltage on the DC side of the receiving-end converter station with the DC voltage reference value; The voltage deviation is processed by a PI controller to generate a d-axis current reference value for the inner current loop. Then, the current loop control generates a modulation signal for the receiving-end converter station to maintain DC voltage stability.

8. The unified architecture voltage and frequency control method for grid-connected energy storage new energy islands via DRU as described in claim 7, characterized in that, The generation of the modulation signal for the receiving-end converter station via current loop control specifically involves: The d-axis current reference value and the preset q-axis current reference value are input into the current inner loop controller; The current inner loop controller generates the AC side voltage reference signal of the receiving-end converter station based on the input current reference value, the feedback AC side current, and the grid voltage phase provided by the phase-locked loop through decoupling control and PI regulation. The AC side voltage reference signal is sent to the PWM modulation unit to generate a pulse control signal to drive the switching devices of the receiving-end converter station.

9. A unified architecture voltage and frequency control system for grid-connected energy storage islands via DRU, characterized in that, The grid-connected energy storage island comprises multiple new energy storage stations and at least one DRU energy storage station installed on the AC bus of the DRU. The voltage and frequency control system includes: The total voltage compensation module is used to obtain the actual power on the DC side of the energy storage station and compare it with the given DC power reference value to obtain the DC power error. The DC power error is then input to the PI controller of the constant DC power loop to generate a total voltage compensation signal. The voltage compensation distribution module is used to input the total voltage compensation signal to the reactive power centralized controller and distribute it according to a preset strategy to obtain the voltage compensation amount of the DRU energy storage station and each new energy energy storage station. A voltage correction module is used for each of the energy storage stations to correct the voltage reference value in its local reactive power-voltage droop control loop according to the voltage compensation amount. The control module is used by each energy storage station to generate modulation signals for its energy storage converters based on the corrected voltage reference value and the frequency reference value generated by its local active power-frequency droop control loop. The module controls the converters according to the modulation signals to achieve constant control of the DC power output from the DRU and distribution control of the reactive power within the DRU output system.

10. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and when the processor executes the computer program, it implements the method as described in any one of claims 1 to 8.

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