Power distribution network topology and regulation method based on transformer area shared energy storage and interconnection

Abstract

A power distribution network topology and regulation method based on transformer area shared energy storage and interconnection, the method installs a converter at the end of each transformer area of a plurality of power distribution networks with loads and distributed power sources, the AC side of the converter is connected to the AC power distribution network, the DC side is connected to the energy storage battery in parallel and through a remote DC switch, a power measurement module is installed at the low voltage side of the power distribution network transformer of each transformer area, the control back office controls each converter and remote DC switch according to the measurement data of each power measurement module, and the local consumption rate of the distributed power source is improved through transformer area shared energy storage and power interconnection, and the returned power of the distributed power source to the upper level power grid is reduced. The power distribution network topology structure of the present application adopts multi-area shared energy storage, and through the power interconnection control mode, the local consumption rate of the distributed power source is greatly improved, the returned power of the distributed power source to the upper level power grid is reduced, the network loss is reduced, and the voltage out-of-limit frequency is also reduced, so that the transformer area voltage is more stable.

Description

Technical Field

[0001] This invention relates to a distribution network control method for shared energy storage and interconnection between different transformer substations, belonging to the field of power transmission and distribution technology. Background Technology

[0002] With the increasing prevalence of renewable distributed power sources (such as distributed photovoltaic power generation equipment), a large number of distributed power sources are being connected to the distribution network, causing the traditional distribution network to gradually evolve into an active distribution network. A high proportion of distributed power sources connected to the distribution network can lead to problems such as voltage exceeding limits and power backflow.

[0003] To address the aforementioned issues, the traditional approach involves installing a certain number of energy storage devices, such as supercapacitors and batteries, in the power distribution network. These devices store energy when the network voltage exceeds its upper limit and release energy when it falls below its lower limit, ensuring stable network operation. For example, patent application CN201610831264.0 discloses an optimized configuration method for the capacity of supercapacitors and batteries in a grid-connected photovoltaic system. This method utilizes two bidirectional converters to control the charging and discharging of the supercapacitor and battery banks respectively. Based on the full lifecycle costs of the supercapacitors, batteries, and converters, a particle swarm optimization algorithm is used to obtain the economical configuration capacity (number of configuration groups) of supercapacitors and batteries that meets the requirements for unbalanced photovoltaic energy storage and release, thereby achieving optimized configuration of supercapacitor and battery capacity. This invention fully considers the operating mode and cost of the converters, incorporating them as independent entities into the optimization calculation of the hybrid energy storage system's configuration capacity. It also considers the constraints of the supercapacitors, batteries, and converters, making the calculation results more scientific and reasonable. This method effectively improves the economic efficiency of photovoltaic power generation systems while ensuring their efficient and stable operation. However, traditional methods regulate individual distribution network areas and cannot improve the installed capacity and local absorption rate of distributed power sources through shared energy storage and interconnection between adjacent areas. Furthermore, some distributed power sources in certain areas transmit significant power back to the upper-level grid, increasing network losses. Therefore, it is necessary for the industry to explore new distribution network topologies and regulation methods. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a distribution network topology and control method based on shared energy storage and interconnection between distribution substations, thereby increasing the installed capacity and local absorption rate of distributed power sources, reducing the power transmitted back to the upper-level grid by distributed power sources, and thus reducing network losses.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A distribution network topology and control method based on shared energy storage and interconnection between distribution substations is proposed. The method involves installing converters at the ends of multiple distribution substations with loads and distributed generation sources. The AC side of the converters is connected to the AC distribution network, and the DC side is connected in parallel and connected to the energy storage battery ES via a remote DC switch QF. A power measurement module is installed at the low-voltage bus of the distribution transformer in each substation. The control backend controls each converter and the remote DC switch based on the measurement data from each power measurement module. By sharing energy storage and power mutual assistance between distribution substations, the local absorption rate of distributed generation sources is improved, and the power fed back from distributed generation sources to the next higher level of the grid is reduced.

[0007] In the above-mentioned distribution network topology and control method based on shared energy storage and interconnection and mutual assistance in distribution areas, the converters of multiple distribution network areas are all connected to the converter control module (PCM). The PCM, the remote DC switch (QF), and the power measurement module are all equipped with wireless communication modules. The control backend receives the measurement data sent by the power measurement module through the wireless network and sends control signals to the remote DC switch (QF) and the PCM through the wireless network.

[0008] The aforementioned distribution network topology and control method based on shared energy storage and interconnection between different distribution areas uses a 4G / 5G communication module.

[0009] The above-mentioned distribution network topology and control method based on shared energy storage and interconnection and mutual assistance in distribution areas, when there are two distribution network areas, the control methods for each converter and remote DC switch are as follows:

[0010] Each distribution network transformer's low-voltage side power measurement module measures the bus power at regular time intervals and transmits the measurement data to the control backend. Let P1 represent the power measurement value of the first distribution area output by the first distribution area power measurement module PM1, and P2 represent the power measurement value of the second distribution area output by the second distribution area power measurement module PM2. pcs1 P represents the power of the first zone converter. pcs2 P represents the power of the second zone converter. ess S represents the charging and discharging power of the energy storage battery. pcs1 Indicates the power limit of the first zone converter; S pcs2 This indicates the power limit of the converter in the second distribution area. Based on the power measurement values ​​of each distribution area, the control backend formulates control strategies to control each converter and the remote DC switch QF.

[0011] a. When P1 < 0; P2 > 0 and |P1| ≤ |P2|, the control backend opens the remote DC switch QF to control the first-zone converter PCS1 and the second-zone converter PCS2, causing power to flow from the first zone to the second zone. The direction of power flow from the first-zone converter PCS1 to the second-zone converter PCS2 is taken as the positive direction of power. The power of each converter is as follows:

[0012] P pcs1 =P pcs2 =|P1|;P ess =0;

[0013] When P1 > 0, P2 < 0, and |P1| ≥ |P2|, the control backend opens the remote DC switch QF to control the first transformer PCS1 and the second transformer PCS2, causing power to flow from the second transformer to the first transformer. The power of each transformer is as follows:

[0014] P pcs1 =P pcs2 =|P2|;P ess =0;

[0015] Constraints: P pcs1 =P pcs2 ≤min{S pcs1 ,S pcs2};

[0016] b. When P1 < 0; P2 > 0 and |P1| > |P2|, the control system closes the remote DC switch QF, transferring a portion of the power fed back from the first transformer area to the second transformer area, while the remaining portion is stored in the energy storage battery. The power of each converter is as follows:

[0017] P pcs1 =|P1|;P pcs2 =|P2|;P ess =|P1|-|P2|;

[0018] When P1 > 0, P2 < 0, and |P1| < |P2|, the control system closes the remote DC switch QF, transferring a portion of the power fed back from the second transformer area to the first transformer area, while the remaining portion is stored in the energy storage battery. The power of each converter is as follows:

[0019] P pcs1 =|P1|;P pcs2 =|P2|;P ess =|P2|-|P1|;

[0020] Constraints: P pcs1 ≤S pcs1 ;P pcs2 ≤S pcs2 ;

[0021] Scenario 3: When P1 < 0 and P2 < 0, the remote DC switch is closed by the control system, and the power returned from the two units is used to charge the energy storage battery. The power of each converter is as follows:

[0022] P pcs1 =|P1|;P pcs2 =-|P2|;P ess =|P1|+|P2|

[0023] Constraints: P pcs1 ≤S pcs1 ;P pcs2 ≤S pcs2 ;

[0024] d. When P1 > 0 and P2 > 0, the remote DC switch is closed by the control system, and the two converters control the AC voltage of their respective transformer areas. The control objective is:

[0025] 0.93pu≤U n ≤1.07pu

[0026] In the formula U n The voltage value at the location where the converter is installed at the end of the nth distribution area;

[0027] Constraints: Energy storage battery discharge: P pcs1 ≤S pcs1 ;P pcs2 ≤S pcs2 The energy storage battery does not discharge: P pcs1 =P pcs2 ≤min{S pcs1 ,S pcs2}

[0028] Beneficial effects

[0029] This invention employs a distribution network topology with shared energy storage across multiple distribution areas. Through control modes such as power mutual assistance, it significantly improves the installed capacity and local absorption rate of distributed power sources, reduces the power transmitted back to the upper-level grid from distributed power sources, lowers network losses, and also reduces the frequency of voltage exceedances, resulting in more stable voltage in the distribution areas. Furthermore, this method reduces the number of charge-discharge cycles for energy storage batteries, which helps extend battery life. Attached Figure Description

[0030] The invention will now be described in further detail with reference to the accompanying drawings.

[0031] Figure 1 This is the low-voltage distribution network wiring diagram used in the embodiments of the present invention;

[0032] Figure 2These are the node and branch numbers of the low-voltage distribution network in this embodiment of the invention, where 1, 2, 3, 4, 5, 6 and 7 are node numbers, and ①, ②, ③, ④, ⑤ and ⑥ are branch numbers.

[0033] The labels in the diagram and text are as follows: T1, distribution network transformer for the first substation; T2, distribution network transformer for the second substation; DG, distributed generation; R, load; PM1, power measurement module for the first substation; PM2, power measurement module for the second substation; PCS1, converter for the first substation; PCS2, converter for the second substation; QF, remote DC switch; ES, energy storage battery; PCM, converter control module; CM, communication module; P1, power measurement value for the first substation; P2, power measurement value for the second substation; P... pcs1 The power of the first zone converter, P pcs2 The power of the second zone converter, P ess Energy storage battery charging and discharging power, S pcs1 The power limit of the first zone converter; S pcs2 The power limit of the second zone converter, U n The voltage value at the location where the converter is installed at the end of the nth distribution area. Detailed Implementation

[0034] This invention provides a distribution network topology and control method based on shared energy storage and interconnection between distribution substations. The primary topology of the distribution network used in this method is as follows: each distribution substation, in addition to carrying a load R (here, load refers to power load), is equipped with distributed generation (DG), such as solar photovoltaic and other new energy power generation equipment. Multiple distribution substations are connected to their respective power conversion systems (PCS). The AC portion of the PCS is connected to the AC distribution network, and the DC portion is connected in parallel with energy storage batteries (ES) installed on the DC side. A remote DC switch (QF) is installed on the output side of the energy storage batteries (ES). That is, the PCS at the ends of multiple distribution substations are interconnected in a back-to-back manner with a common DC bus. The DC bus is connected to the energy storage batteries (ES) via the remote DC switch (QF). The remote DC switch (QF) and the converter control module (PCM) connected to each PCS receive control signals from the control backend via a wireless network.

[0035] The secondary topology of the distribution network is as follows: a power measurement module is installed at the low-voltage side bus of the distribution network transformer in each distribution area. The power measurement module is equipped with a communication module based on 4G / 5G (and other communication methods). The power data output by the power measurement module is sent to the control backend through the communication module. The control backend analyzes and processes the data in real time to generate control signals for each converter and remote DC switch.

[0036] When the remote DC switch QF is open, multiple converter PCS operate in power balance mode to balance the power imbalance between different distribution areas, transfer the power fed back from the distribution area to the distribution area with a larger load level, or balance the load levels between different distribution areas, thereby reducing network losses, improving voltage quality, and reducing the power fed back.

[0037] If, under power sharing mode, the distribution area still cannot absorb the power generated by distributed generation (with power fed back to the upper-level grid) or cannot balance the load between distribution areas, the remote DC switch QF closes. Through the charging and discharging of the energy storage battery ES, the fed-back power and the imbalance between distribution areas are further optimized. In this case, the energy storage battery exists as a shared energy storage device between distribution network distribution areas.

[0038] In the power mutual assistance mode of the distribution area, the energy storage battery ES is not connected. Some of the converter PCS operate in constant DC side voltage (and AC reactive power control) mode, while the remaining converter PCS adopt PQ control mode (i.e., power control mode, controlling the output active and reactive power to meet the load demand). After the remote DC switch QF is closed, the energy storage battery ES also participates in the system's power regulation. At this time, all converter PCS operate in PQ (and current limiting) control mode, and the DC side voltage level of the converter depends on the battery voltage.

[0039] The control process of each converter and remote DC switch is as follows: Based on the measurement values ​​of the power measurement module on the low-voltage side of the distribution transformer in each area, the power of the back-to-back converter PCS interconnection and sharing is first determined, so as to realize the local consumption of distributed power in multiple areas without the intervention of the energy storage battery ES.

[0040] When distributed power sources (such as photovoltaic power generation equipment) from multiple distribution areas cannot be fully absorbed through interconnection and mutual assistance, the remote DC switch QF closes, and the energy storage battery ES is used to charge and improve the absorption of distributed power sources, ultimately achieving the goal of minimizing or even eliminating the return of power. When the load level of a distribution area is high and the output of distributed power sources is low (for example, the photovoltaic power generation equipment generates less power in the evening or at night), the distribution area may experience voltage exceeding the lower limit. In this case, if the loads of two distribution areas are unbalanced (one distribution area is heavily loaded and the other is lightly loaded), the first consideration is to achieve load power balance between distribution areas through power mutual assistance. If the problem of voltage exceeding the lower limit still exists, the remote DC switch closes, and the voltage level of the distribution area node is improved by discharging the energy storage battery ES.

[0041] This invention fully utilizes the complementary characteristics of inter-transformer loads and distributed power sources, solving the problems of low absorption capacity and low voltage levels of distributed generation in the transformer substation. At the same time, it reduces the capacity and number of charge / discharge cycles of energy storage batteries, extends the service life of energy storage batteries, and reduces energy storage investment.

[0042] The following uses two districts as examples to explain in detail the control steps of the converter and remote DC switch:

[0043] The low-voltage side power measurement module of the distribution network transformer measures the bus power at regular time intervals (e.g., 3 seconds) and transmits the measurement data to the control backend via a communication module based on 4G / 5G (and other communication methods). Based on the power measurement values ​​of different distribution areas, the control backend formulates control strategies to control the converter PCS and the remote DC switch QF on the energy storage battery side. Let P1 represent the power measurement value of the first distribution area output by the first distribution area power measurement module PM1, and P2 represent the power measurement value of the second distribution area output by the second distribution area power measurement module PM2. The control strategies under different load and distributed power output scenarios are as follows:

[0044] Scenario 1: Two transformer substations have opposite power measurements, one positive and one negative, and both substations consume positive power. Power backflow is absorbed through power exchange between the two substations. For example, when P1 < 0; P2 > 0 and |P1| ≤ |P2| (both substations consume positive power, and power backflow to the upper-level grid is negative), it indicates that the first substation is backflowing power, the second substation is consuming power, and the power consumed by the second substation is greater than or equal to the power backflow from the first substation. Both substations consume positive power. The control strategy in this scenario is to absorb the backflow through power exchange between the two substations. Specifically, the control system opens the remote DC switch QF to control the converters PCS1 and PCS2 in both substations, allowing power to flow from the first substation to the second substation. The direction of power flow from PCS1 in the first substation to PCS2 in the second substation is considered the positive power direction (this will be used as a reference direction in subsequent scenarios). The power values ​​of each converter are as follows:

[0045] P pcs1 =P pcs2 =|P1|;P ess =0

[0046] In the formula P pcs1 P represents the power of the first zone converter. pcs2 P represents the power of the second zone converter. ess Indicates the charging and discharging power of the energy storage battery;

[0047] Considering the power constraints of the converter: the power limit of the converter in the first area is S. pcs1 The power limit for the second inverter is S. pcs2 The power exchanged between transformer substations must not exceed the power limit of the converter: min{S pcs1 ,S pcs2}

[0048] If |P2|≥|P1|>min{S pcs1 ,S pcs2}; then we have: Ppcs1 =P pcs2 =min{S pcs1 ,S pcs2}

[0049] Similarly, when P1 > 0, P2 < 0, and |P1| ≥ |P2|, the control backend opens the remote DC switch QF to control the first transformer PCS1 and the second transformer PCS2, so that power flows from the second transformer to the first transformer. The power of each transformer is as follows:

[0050] P pcs1 =P pcs2 =|P2|;P ess =0;

[0051] Constraints: P pcs1 =P pcs2 ≤min{S pcs1 ,S pcs2};

[0052] Scenario 2: Two transformer substations have opposite power measurements, one positive and one negative, and both substations consume negative power. A portion of the power fed back from one substation is transferred to the other, while the remainder is stored in the energy storage battery. For example, if P1 < 0, P2 > 0, and |P1| > |P2|, it indicates that the first substation is feeding back power, the second substation is consuming power, and the first substation's fed-back power is greater than the second substation's power consumption. The control strategy for this scenario is a power mutual assistance + energy storage charging mode. A remote DC switch is closed, transferring a portion of the power fed back from the first substation to the second substation, while the remainder is stored in the energy storage battery.

[0053] P pcs1 =|P1|;P pcs2 =|P2|;P ess =|P1|-|P2|

[0054] Similarly, when P1 > 0, P2 < 0, and |P1| < |P2|, the remote DC switch QF is closed by the control backend to transfer a portion of the power fed back from the second transformer area to the first transformer area, while the other portion is stored by the energy storage battery. The power of each converter is as follows:

[0055] P pcs1 =|P1|;P pcs2 =|P2|;P ess =|P2|-|P1|;

[0056] Constraints:

[0057] P pcs1 ≤S pcs1 ;P pcs2 ≤S pcs2 .

[0058] Scenario 3: When P1 < 0 and P2 < 0, it means that both transformer areas are feeding back power under this scenario. The control strategy is to close the remote DC switch, and the power fed back from both transformer areas will charge the energy storage battery and absorb the fed-back power.

[0059] P pcs1 =|P1|;P pcs2 =-|P2|;P ess =|P1|+|P2|

[0060] Constraints:

[0061] P pcs1 ≤S pcs1 ;P pcs2 ≤S pcs2 .

[0062] Scenario 4: When P1 > 0 and P2 > 0, it indicates that both distribution areas are consuming power, and the control objective is to improve the voltage quality at the end of the distribution network. The voltage value of the AC section of the converter can be measured through the control loop. Distribution areas with higher load rates experience relatively larger voltage drops, which can be addressed by power rebalancing or a power rebalancing + energy storage battery discharge mode to improve the voltage quality of the distribution network.

[0063] Control target (taking a 380V transformer substation as an example):

[0064] 0.93pu≤U n ≤1.07pu

[0065] In the formula U n The voltage value at the location where the converter is installed at the end of the nth transformer substation; constraints:

[0066] Energy storage battery discharge: P pcs1 ≤S pcs1 ;P pcs2 ≤S pcs2

[0067] Energy storage battery does not discharge: P pcs1 =P pcs2 ≤min{S pcs1, S pcs2}

[0068] This invention fully utilizes the flexibility of converter control, increasing the absorption of distributed power through inter-distribution power complementarity. When inter-distribution power complementarity cannot be fully realized, energy storage is added to enhance control flexibility. Compared to installing energy storage in a single distribution area, shared energy storage between distribution areas reduces the number of charge-discharge cycles of the energy storage batteries, thus extending their lifespan. Absorbing fed-back power contributes to voltage stability in the distribution area and reduces the occurrence of voltage exceedances.

[0069] The topology based on shared energy storage and interconnected distribution networks is as follows: Figure 1 As shown (taking two transformer substations in a low-voltage distribution network as an example). A power measurement module (with a communication module) is installed at the 0.4kV busbar of the transformer substation. The measured busbar power is transmitted to the control backend via a 4G / 5G (and other communication methods) network. The control side of the remote DC switch and converter is equipped with a communication module to receive control signals from the control backend. The control backend determines the control mode based on the busbar power value of the transformer substation. The control signal ultimately controls the power transmission of the converter via the converter control module (PCM).

[0070] The following is based on Figure 2 The wiring diagram serves as a case study to illustrate the specific implementation of the control strategy.

[0071] In the first distribution area, nodes 2, 4, and 6 are load nodes, and nodes 3, 5, and 7 are distributed generation (DG) connection points. Each load node has a load of 20kW, and each DG has a power output of 30kW. In the second distribution area, nodes 2, 4, 6, and 7 are load nodes, and nodes 3 and 5 are DG connection points. Each load node has a load of 40kW, and each DG has a power output of 40kW. The total installed capacity of DG in the first distribution area exceeds the load size, while the total installed capacity of DG in the second distribution area is less than the load size. For DG connected to the low-voltage distribution network, due to user considerations regarding grid-connected power revenue from energy storage batteries, photovoltaic (PV) power generation equipment typically operates in MPPT mode with a power factor of 1. Therefore, it is considered that the PV power generation equipment only generates active power. The distribution area line parameters are shown in Table 1.

[0072] Table 1. Transformer Area Line Parameters

[0073]

[0074] The following examples discuss different scenarios:

[0075] Table 2. Examples of Control Strategies

[0076]

[0077]

[0078] Mode 1: At this time, the measured power values ​​of both the first and second transformer substations are positive, indicating that both substations are absorbing power from the upstream power grid. This mode corresponds to Scenario 4. Next, determine if there is a voltage limit violation at the end nodes: the voltage at the end of the first transformer substation is 1.0369 pu; the voltage at the end of the second transformer substation is 1.0267 pu (the voltage range of the low-voltage distribution network is 0.93-1.07 pu), therefore, the voltages of both substations are within limits. At this time, the converter and the energy storage DC remote switch do not operate.

[0079] Mode 2: In this mode, the measured power of the first transformer area is -50kW, indicating that the photovoltaic output exceeds the load, resulting in power backflow. The measured power of the second transformer area is 120kW, indicating that the load exceeds the photovoltaic output, thus the overall load characteristic is power absorption. The measured power is alternating between positive and negative values, with P1 < 0 and P2 > 0, and |P1| < |P2|. This mode corresponds to Scenario 1, where back-to-back converters transfer 50kW of power from the first transformer area to the second. The power backflow problem is resolved through inter-transformer power exchange; the energy storage battery does not participate in this process.

[0080] Mode 3: In this mode, the measured power of the first and second transformer areas is opposite, with P1 < 0 and P2 > 0, and |P1| > |P2|. This mode corresponds to Scenario 2. Firstly, a portion of the power fed back from the first transformer area is transferred to the second transformer area via back-to-back converters. The portion of power fed back that cannot be resolved through transformer area transfer is absorbed by the energy storage battery. pcs1 =50kW; P pcs2 =40kW; P ess =10kW. The first transformer area mutually supports the second transformer area with a power of 40kW, and the energy storage battery consumes 10kW.

[0081] Mode 4: In this mode, the measured power values ​​for both the first and second photovoltaic (PV) zones are negative, indicating that both zones are feeding power back to the grid. The photovoltaic output of both zones exceeds the load. This mode corresponds to Scenario 3. Excess photovoltaic power is absorbed by charging the energy storage battery. pcs1 =70kW; P pcs2 =-40kW; P ess =110kW. The energy storage battery is charged through the first regional inverter PCS1 and the second regional inverter PCS2, and the charging power is the sum of the absolute values ​​of the two.

[0082] Mode 5: Both the first and second transformer substations have positive measured power values, indicating that both substations are absorbing power from the grid. This mode corresponds to Scenario 4. In this case, voltage levels are improved by adjusting the power at the terminals. Terminal voltage of the first substation: 1.3069 pu; Terminal voltage of the second substation: 0.9108 pu. The voltage of the first substation has exceeded the upper limit, and the voltage of the second substation has exceeded the lower limit. Therefore, power is transferred from the first substation to the second substation. P pcs1 =20kW; P pcs2 =20kW. At this time, the voltage at the end of the first transformer area is 1.0129pu; the voltage at the end of the second transformer area is 0.933pu, both of which meet the voltage limit.

[0083] As can be seen from the above examples, the shared energy storage strategy based on distribution network can effectively solve the problem of power fed back from the distribution network to the upper-level grid. Power feeding back is generally accompanied by voltage over-limit situations, which has a serious impact on the safe and stable operation of the system and will also accelerate the aging of electrical equipment insulation and reduce its lifespan. By using the control strategy of shared energy storage, the voltage over-limit problem can be greatly alleviated. Taking mode 2-4 in Table 2 as an example, the voltage values ​​before and after control are calculated (see Table 3) to further verify the improvement of voltage by the control strategy.

[0084] Table 3 Voltage values ​​before and after adjustment

[0085]

[0086] According to the data in Table 3, the highest voltage at nodes in modes 2, 3, and 4 of the first distribution area had exceeded the limit before regulation (the voltage range of the low-voltage distribution network is 0.93-1.07 pu). After the interconnection and mutual assistance of converters and the shared energy storage regulation, the highest voltage values ​​all met the voltage requirements of the low-voltage distribution network. Observe the highest voltage value U in the table. high With the lowest value U low After regulation, no cases of excessively high or low voltage occurred. Therefore, the regulation strategy based on shared energy storage and interconnection and mutual assistance between distribution transformer areas can not only reduce or even eliminate voltage exceedance situations, but also improve the voltage quality of the distribution transformer areas.

Claims

1. A distribution network topology control method based on shared energy storage and interconnection and mutual assistance in distribution areas, characterized in that, The method involves installing converters at the ends of multiple distribution network areas with loads and distributed power sources. The AC side of the converters is connected to the AC distribution network, and the DC side is connected in parallel and connected to the energy storage battery (ES) through a remote DC switch (QF). A power measurement module is installed at the low-voltage bus of the distribution network transformer in each area. The control backend controls each converter and the remote DC switch based on the measurement data of each power measurement module. By sharing energy storage and power mutual assistance among the distribution areas, the local absorption rate of distributed power sources is improved, and the power fed back to the upper-level grid by distributed power sources is reduced. When there are two distribution network areas, the control methods for each converter and remote DC switch are as follows: The low-voltage side power measurement modules of the distribution network transformers in each area measure the bus power at regular time intervals and transmit the measurement data to the control backend; This indicates the power measurement value of the first substation output by the first substation power measurement module (PM1). This indicates the power measurement value of the second substation output by the second substation power measurement module (PM2). This indicates the power of the first zone converter. This indicates the power of the second zone converter. Indicates the charging and discharging power of the energy storage battery. Indicates the power limit of the first zone converter; This indicates the power limit of the converter in the second transformer area. Based on the power measurement values ​​of each transformer area, the control backend formulates control strategies to control each converter and the remote DC switch (QF). Scenario 1: When ; and At that time, the control backend opens the remote DC switch (QF) to control the first zone converter (PCS1) and the second zone converter (PCS2), so that power flows from the first zone to the second zone. The direction of power flow from the first zone converter (PCS1) to the second zone converter (PCS2) is taken as the positive direction of power. The power of each converter is as follows: ； ； when ; and At that time, the control backend opens the remote DC switch (QF) to control the first zone converter (PCS1) and the second zone converter (PCS2), so that power flows from the second zone to the first zone. The power of each converter is as follows: ； ； Constraints: ; Scenario 2: When ; and At that time, the control backend closes the remote DC switch (QF), transferring a portion of the power fed back from the first transformer area to the second transformer area, while the remaining portion is stored by the energy storage battery. The power of each converter is as follows: ； ； ； when ; and At that time, the control backend closes the remote DC switch (QF), transferring a portion of the power fed back from the second transformer area to the first transformer area, while the remaining portion is stored by the energy storage battery. The power of each converter is as follows: ； ； ； Constraints: ; ; Scenario 3: When ; At that time, the control backend closes the remote DC switch (QF), and the two regional power feedback units charge the energy storage battery and absorb the feedback power. The power of each converter is as follows: ； ； Constraints: ; ; Scenario 4: When ; At that time, the remote DC switch (QF) is closed by the control backend, and the two converters control the AC voltage of their respective distribution areas. The control objective is: In the formula The voltage value at the location where the converter is installed at the end of the nth distribution area; Constraints: Energy storage battery discharge: P pcs1 ≤S pcs1 ;P pcs2 ≤S pcs2 The energy storage battery does not discharge: P pcs1 =P pcs2 ≤min{S pcs1 ,S pcs2 } 2. The distribution network topology control method based on shared energy storage and interconnection and mutual assistance in transformer substations as described in claim 1, characterized in that, The converters in multiple distribution network areas are all connected to the converter control module (PCM). The converter control module (PCM), the remote DC switch (QF), and the power measurement module are all equipped with wireless communication modules. The control backend receives the measurement data sent by the power measurement module through the wireless network and sends control signals to the remote DC switch (QF) and the converter control module (PCM) through the wireless network.

3. The distribution network topology control method based on shared energy storage and interconnection and mutual assistance in transformer substations as described in claim 2, characterized in that, The wireless communication module is a 4G / 5G communication module.

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