Power coordination and voltage support control method and related device

Abstract

The invention discloses a power coordination and voltage support control method and a related device, and relates to the technical field of power distribution system control, and the method comprises the steps: building a basic control model of a multi-port flexible interconnection system, and according to the comparison relation between the real-time charge state of an energy storage battery and the preset safety working interval of the energy storage battery, calculating the real-time charge state of the energy storage battery; determining a current optical storage cooperative basic working mode of the multi-port flexible interconnection system; determining the current operation state of the multi-port flexible interconnection system according to the connection state of each AC port and the DC side in the multi-port flexible interconnection system and the feeder line working condition; and carrying out power coordination and voltage support control on the basis of the basic control model in combination with the optical storage coordination basic working mode and the operation state, thereby generating an actual power instruction of each inverter so as to realize power coordination and voltage support of the multi-port flexible interconnection system. According to the invention, the problems of insufficient power coordination capability, insufficient voltage supporting capability and poor mode switching stability and reliability in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of power distribution system control technology, and in particular to a power coordination and voltage support control method and related apparatus. Background Technology

[0002] With the increasing proportion of new energy sources, photovoltaic (PV) power generation systems are gradually becoming an important component of microgrids. Most existing PV inverters operate at maximum power point (MPP). In this mode, when there are changes in sunlight or load fluctuations, the PV output power is momentarily insufficient, and the inverter cannot quickly respond to changes in DC-side voltage, leading to a drop in DC bus voltage, fluctuations in AC bus voltage, and frequency drift and instability in the system. To address the voltage support and frequency control issues, researchers have proposed voltage source droop control strategies, where the inverter directly executes droop control, and the DC / DC converter is responsible for maintaining DC bus voltage stability. This control scheme sacrifices some PV output power to give the inverter some voltage support and frequency regulation characteristics. However, the above control strategies have the following drawbacks under conditions of no energy storage or low energy storage charge: they cannot respond to load in real time to achieve power balance. Since the DC bus voltage is entirely regulated by the DC / DC converter, the DC / DC converter needs to handle disturbances from the source side. Under power shortage conditions, the PV output power cannot meet the load demand, at which point it completely loses its DC-side voltage regulation capability.

[0003] In summary, current multi-port flexible interconnection systems mainly achieve bidirectional power flow between distribution stations through flexible interconnection devices. However, existing technologies generally suffer from the following defects and shortcomings: 1) Insufficient power coordination capability: Existing systems mostly adopt master-slave control or fixed power allocation modes, failing to consider the fluctuations in distributed photovoltaic output, energy storage state of charge, and load differences at each port. This leads to unbalanced power distribution, and some feeders are prone to overload or reverse power flow problems. 2) Insufficient voltage support capability: Most control strategies only achieve voltage regulation at one end or locally, lacking a globally coordinated voltage support mechanism. When the power flow direction switches or the interconnection system operating mode changes, the DC bus voltage is prone to sudden changes, even causing voltage collapse or system oscillation. 3) Poor mode switching stability and reliability: Existing methods often lack hysteresis zones and judgment logic when switching between modes such as distribution station interconnection, islanding, and fault transfer, resulting in frequent switching and repeated oscillations in power flow direction, affecting system stability and equipment lifespan. Summary of the Invention

[0004] This invention provides a power coordination and voltage support control method and related apparatus to solve the problems of insufficient power coordination capability, insufficient voltage support capability, and poor mode switching smoothness and reliability in the prior art.

[0005] In view of this, a first aspect of the present invention provides a power coordination and voltage support control method, the method comprising:

[0006] A basic control model for a multi-port flexible interconnection system is established. The basic control model includes: a voltage control and power balance model based on DC voltage, a dynamic model of the inverter DC side based on virtual inertia, and a power regulation relationship based on droop characteristics.

[0007] Based on the comparison between the real-time state of charge of the energy storage battery and the preset safe operating range of the energy storage battery, the current basic working mode of photovoltaic-energy storage collaboration of the multi-port flexible interconnection system is determined.

[0008] Based on the connection status of each AC port and DC side and the feeder operating condition in the multi-port flexible interconnection system, the current operating status of the multi-port flexible interconnection system is determined.

[0009] Based on the aforementioned basic control model, and combined with the aforementioned photovoltaic-storage collaborative basic working mode and operating status, power coordination and voltage support control are performed to generate and output the actual power commands of each inverter, thereby realizing the power coordination and voltage support of the multi-port flexible interconnection system.

[0010] Optionally, the process of establishing the DC-side dynamic model of the inverter based on virtual inertia includes:

[0011] An energy balance equation containing a virtual angular frequency and DC-side voltage is constructed for the i-th inverter. A virtual inertia parameter is introduced into the equation to characterize the inertial response characteristics of the inverter, so as to obtain the DC-side dynamic model of the inverter based on virtual inertia.

[0012] Optionally, the process of establishing the power regulation relationship based on droop characteristics includes:

[0013] A droop relationship between the virtual angular frequency and active power is established, and based on the droop relationship and the small-signal linearization model of DC voltage, a reference power regulation law for adjusting photovoltaic cells and energy storage batteries is derived to obtain the power regulation relationship based on the droop characteristic.

[0014] Optionally, the preset safe operating range of the energy storage battery is between 80% and 20% of its real-time state of charge; the basic working mode of photovoltaic-energy storage collaboration includes:

[0015] When the real-time state of charge is within the safe operating range, the photovoltaic system operates in maximum power point tracking mode, and the energy storage battery is charged and discharged on demand.

[0016] When the real-time state of charge is lower than 20% of the real-time state of charge limit, the photovoltaic system operates in maximum power point tracking mode, and the energy storage battery is prohibited from discharging.

[0017] When the real-time state of charge is higher than 80% of the upper limit of the real-time state of charge, the photovoltaic system switches to a power-limited operation mode, and the energy storage battery is prohibited from charging.

[0018] Optionally, the basic working mode of optical-storage collaboration can be combined with the current operating state of the multi-port flexible interconnection system to form several coordinated control sub-modes;

[0019] Each of the aforementioned coordinated control sub-modes corresponds to a preset power balance equation, which is used to determine the power distribution relationship between photovoltaics, energy storage batteries, inverters and AC distribution networks under preset real-time state of charge constraints and preset operating conditions.

[0020] Optionally, the current operating state of the determined multi-port flexible interconnection system includes one of the following three types:

[0021] Normal interconnection status: All AC ports are connected to the DC side for operation;

[0022] Power transfer status: At least one AC port is disconnected from the DC side due to fault or maintenance, and its original power supply load is transferred to the remaining normal ports through a flexible interconnection device;

[0023] Emergency state: All AC ports are disconnected from the DC side and are in an islanded state. The DC side provides short-term emergency power supply to preset critical loads.

[0024] Optionally, the power coordination and voltage support control are further included before:

[0025] Calculate the critical redundancy power of the multi-port flexible interconnection system, determine the operating status of the multi-port flexible interconnection system based on the critical redundancy power, and cut off the preset non-critical loads when the operating status is in a deficit state.

[0026] A second aspect of the present invention provides a power coordination and voltage support control system, the system comprising:

[0027] A modeling unit is established to build the basic control model of a multi-port flexible interconnection system. The basic control model includes: a voltage control and power balance model based on DC voltage, a dynamic model of the inverter DC side based on virtual inertia, and a power regulation relationship based on droop characteristics.

[0028] The first design unit is used to determine the current basic working mode of the multi-port flexible interconnection system for photovoltaic-storage collaboration based on the comparison between the real-time state of charge of the energy storage battery and the preset safe working range of the energy storage battery.

[0029] The second design unit is used to determine the current operating status of the multi-port flexible interconnection system based on the connection status of each AC port to the DC side and the feeder operating conditions in the multi-port flexible interconnection system.

[0030] The control unit is used to perform power coordination and voltage support control based on the basic control model, combined with the basic working mode of photovoltaic-storage collaboration and the operating state, thereby generating and outputting the actual power commands of each inverter to realize the power coordination and voltage support of the multi-port flexible interconnection system.

[0031] A third aspect of the present invention provides a power coordination and voltage support control device, the device comprising a processor and a memory:

[0032] The memory is used to store program code and transmit the program code to the processor;

[0033] The processor is configured to execute the steps of the power coordination and voltage support control method as described in the first aspect above, according to the instructions in the program code.

[0034] A fourth aspect of the present invention provides a computer-readable storage medium for storing program code for executing the power coordination and voltage support control method described in the first aspect above.

[0035] As can be seen from the above technical solutions, the present invention has the following advantages:

[0036] This invention provides a power coordination and voltage support control method. By introducing DC-side voltage feedback to establish virtual inertia, it achieves voltage self-support and power balance control of the inverter. By introducing a photovoltaic-storage collaborative control strategy that considers the safe operating range of energy storage batteries and a power coordination control strategy for multi-port flexible interconnection systems, it achieves distributed flexible interconnection and adaptive power allocation, significantly improving the flexibility of power flow distribution and the overall energy utilization rate of the system. Simultaneously, the system can automatically rebalance power through frequency offset, thus maintaining voltage and frequency stability under light fluctuations or load disturbances. In summary, this invention significantly improves the stability, practicality, and economy of multi-port flexible interconnection power distribution systems. It thus solves the problems of insufficient power coordination capability, insufficient voltage support capability, and poor mode switching smoothness and reliability in existing technologies. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A flowchart illustrating a power coordination and voltage support control method provided in an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of the structure of a multi-port flexible interconnection system (i.e., a multi-port flexible interconnection distribution network) provided in an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of a power coordination and voltage support control system provided in an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] Please see Figure 1 The present invention provides a power coordination and voltage support control method, comprising:

[0043] Step 101: Establish the basic control model of the multi-port flexible interconnection system. The basic control model includes: a voltage control and power balance model based on DC voltage, a dynamic model of the inverter DC side based on virtual inertia, and a power regulation relationship based on droop characteristics.

[0044] In one embodiment, the process of establishing a DC voltage-based voltage control and power balance model includes:

[0045] Please see Figure 2 , Figure 2 in, u g1 u g2 These are the AC bus voltages at AC ports 1 and 2 respectively (this parameter will not be discussed further in the following content), and the middle section is the LCL filter section (this parameter will not be discussed further in the following content). o Given the DC bus voltage, and based on the circuit structure shown in the diagram, the DC side of the multi-port flexible interconnected power distribution system is analyzed. According to KCL, we have:

[0046] ;

[0047] In the formula, This is the parallel value of the DC-side capacitors. The DC bus voltage is given by t, where t is time. This is the DC side current of inverter 1. This is the DC side current of inverter 2. The current output from the photovoltaic cell via the DC / DC converter. This refers to the current output from the energy storage battery via a DC / DC converter.

[0048] Where C is the sum of the parallel DC capacitors, and both sides of the equation are multiplied by U. o We can obtain:

[0049] ;

[0050] In the formula, This is the parallel value of the DC-side capacitors. The voltage is the DC bus voltage, and t is time. Input power to inverter 1 Input power for inverter 2 The output power of photovoltaic cells via DC / DC converter The power output of the energy storage battery via a DC / DC converter.

[0051] It can be seen that if the DC bus voltage fluctuates, a power imbalance will occur. Further transformation yields:

[0052] ;

[0053] ;

[0054] In the formula, ki (i.e., k1 and k2) are proportionality coefficients. This is the parallel value of the DC-side capacitors. This is the DC-side bus voltage. It is the square of the difference between the actual value and the rated value of the DC bus voltage. Input power to inverter 1 Input power for inverter 2 The output power of photovoltaic cells via DC / DC converter The power output of the energy storage battery via a DC / DC converter.

[0055] Setting k1 equal to k2, we obtain the voltage control and power balance model based on DC voltage as follows:

[0056] ;

[0057] In the formula, ki (i.e., k1 and k2) are proportionality coefficients, and P refi P is the reference output power of inverter i. vsci This represents the actual output power of inverter i (introduced in subsequent steps). This leads to the DC-side ΔU. o 2 As a compensation measure, the inverter can quickly track the DC bus voltage.

[0058] In one embodiment, the process of establishing a dynamic model of the DC side of an inverter based on virtual inertia includes:

[0059] An energy balance equation containing virtual angular frequency and DC-side voltage is constructed for the i-th inverter. A virtual inertia parameter is introduced into the equation to characterize the inertial response characteristics of the inverter, so as to obtain a DC-side dynamic model of the inverter based on virtual inertia.

[0060] Specifically, for the DC-side voltage u of the i-th inverter o,i Virtual angular frequency The energy balance equation (i.e., the DC-side dynamic model of the inverter based on virtual inertia) is established as follows:

[0061] ;

[0062] In the formula, For the input power of the i-th inverter, Let be the output power of the i-th inverter. This is the virtual inertia of inverter i.

[0063] In one embodiment, the process of establishing a power regulation relationship based on droop characteristics includes:

[0064] A droop relationship between virtual angular frequency and active power is established. Based on the droop relationship and a small-signal linearization model of DC voltage, a reference power regulation law for adjusting photovoltaic cells and energy storage cells is derived to obtain a power regulation relationship based on droop characteristics.

[0065] Specifically, the power regulation relationship based on droop characteristics is first established as follows:

[0066] ;

[0067] Next, through small-signal linearization, the relationship between the DC-side voltage and the angular frequency is obtained as follows:

[0068] ;

[0069] The reference power regulation laws for photovoltaic cells and energy storage batteries (i.e., power regulation relationships based on droop characteristics) are obtained as follows:

[0070] ;

[0071] ;

[0072] In the formula, This is the adjustment value for the active power reference of photovoltaic cell i. This is the active power reference power adjustment value for energy storage battery i. For photovoltaic active power controller, for Inverter droop factor, U is the reference frequency. o This is the rated voltage on the DC side of the inverter.

[0073] Step 102: Based on the comparison between the real-time state of charge of the energy storage battery and the preset safe operating range of the energy storage battery, determine the current basic working mode of photovoltaic-energy storage collaboration of the multi-port flexible interconnection system.

[0074] In one embodiment, the preset safe operating range of the energy storage battery is between 80% of the upper limit of the real-time state of charge and 20% of the lower limit of the real-time state of charge.

[0075] It should be noted that this invention maintains the state of charge (SOC) of the energy storage battery between 20% and 80% to ensure safe operation and maximize its lifespan. That is:

[0076] ;

[0077] ;

[0078] In the formula, SOC represents the state of charge of the energy storage battery, which can be determined from the power balance of the system (i.e., the multi-port flexible interconnection system, which will be abbreviated as "system" below for ease of description):

[0079] ;

[0080] In the formula, P AC1 For the output power of AC distribution network 1, P AC2 For the output power of AC distribution network 2, P L1 P is the power required for AC load 1. L2 P is the power required for AC load 2. pv P is the output power of the photovoltaic cell. bat This refers to the output power of the energy storage battery.

[0081] When the system input power exceeds the output power and the SOC reaches 80%, the output power of the photovoltaic cells needs to be limited. At this time:

[0082] ;

[0083] In the formula, P pv P represents the actual output power of the photovoltaic cell. pvMax P represents the maximum output power of the photovoltaic system. pvLim Limiting photovoltaic power.

[0084] Therefore, based on the state of charge of the energy storage battery, this invention proposes three operating modes to realize a photovoltaic-energy storage coordinated control strategy. The basic photovoltaic-energy storage coordinated operating modes include:

[0085] Mode 1: When the real-time state of charge is within the safe operating range, the photovoltaic system operates in maximum power point tracking mode, and the energy storage battery charges and discharges on demand.

[0086] Specifically, the photovoltaic module operates at its maximum power point when the energy storage battery's state of charge is within a safe range. The inverter operates according to the given commanded power P. ref Output active power. The SOP (Flexible Interconnected Unit, referring to a device composed of inverters (i.e., converters, VSCs) provides active power and frequency support to the system, while simultaneously enabling full absorption of distributed photovoltaic power output. The relationship between the VSC power command value and the system power flow is as follows:

[0087] ;

[0088] ;

[0089] ;

[0090] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc P represents the actual output power of the inverter. ref This is the inverter's reference output power.

[0091] Mode 2: When the real-time state of charge is 20% below the real-time state of charge limit, the photovoltaic system operates in maximum power point tracking mode, and the energy storage battery is prohibited from discharging.

[0092] Specifically, when the state of charge of the energy storage battery reaches the safe lower limit, if the photovoltaic output power is greater than the inverter's reference output power at this time, in order to avoid over-discharge of the energy storage battery, the energy storage battery will not discharge when the power does not fluctuate significantly. The power flow relationship is as follows:

[0093] ;

[0094] ;

[0095] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required for AC load 1. L2 P is the power required for AC load 2. vsc P represents the actual output power of the inverter. ref P is the inverter reference output power. pv This represents the actual output power of the photovoltaic cell.

[0096] Mode 3: When the real-time state of charge is higher than 80% of the real-time state of charge limit, the photovoltaic system switches to power-limited operation mode, and the energy storage battery is prohibited from charging.

[0097] Specifically, when the energy storage battery reaches its safe state of charge limit, if the photovoltaic output power equals the inverter's reference output power, to prevent overcharging of the energy storage battery, the power flow relationship is as follows, and the photovoltaic output power needs to be limited:

[0098] ;

[0099] ;

[0100] ;

[0101] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required for AC load 1. L2 P is the power required for AC load 2. vsc P represents the actual output power of the inverter. ref P is the inverter reference output power. pv P represents the actual output power of the photovoltaic cell. pvMax P represents the maximum output power of the photovoltaic system. pvLim Limiting photovoltaic power.

[0102] It should be noted that the above control strategy can effectively improve the cycle life of the energy storage battery, maximize the absorption of photovoltaic cell output power, and ensure that the energy storage battery still has the ability to absorb or output fluctuating power when the photovoltaic output power or load fluctuates.

[0103] Furthermore, in one embodiment, the basic working mode of optical-storage collaboration is combined with the current operating state of the multi-port flexible interconnection system to form several coordinated control sub-modes;

[0104] Each coordinated control sub-mode corresponds to a preset power balance equation. The power balance equation is used to determine the power distribution relationship between photovoltaics, energy storage batteries, inverters and AC distribution network under preset real-time state of charge constraints and preset operating conditions.

[0105] It should be noted that the three patterns (pattern 1, pattern 2, and pattern 3) mentioned above can be further broken down into the following:

[0106] Mode 1-1: The system is in normal interconnection state, and the transmission power of each power conversion unit does not exceed the rated limit. The photovoltaic cells employ MPPT (Maximum Power Point Tracking) control to achieve efficient utilization of distributed renewable energy, and the batteries perform charging and discharging operations within their safe operating range; the load P... L1 With load P L2 Both are in a stable power supply state; power exchange is achieved between distribution networks 1 and 2 through converters VSC1 and VSC2 to realize load balancing of feeders 2, i.e.:

[0107] ;

[0108] ;

[0109] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required for AC load 1. L2 P is the power required for AC load 2. vsc P represents the actual output power of the inverter. ref P is the inverter reference output power. pv P represents the actual output power of the photovoltaic cell. bat P represents the actual output power of the energy storage battery. vsci P represents the actual output power of inverter i. Li P represents the actual power required by load i. aci The actual output power of the AC distribution network.

[0110] Mode 1-2: The system is in a power transfer state, and the transmission power of each power conversion unit does not exceed the rated limit. The photovoltaic cells use MPPT control to achieve efficient utilization of distributed new energy, and the batteries perform charging and discharging operations within their safe operating range. Due to factors such as a fault in the AC distribution network 1 feeder, a transformer fault in the distribution area, and distribution network maintenance, AC port 1 is in an off-grid state. The DC distribution area and AC distribution network 2 transfer power to AC load 1 based on port power distribution to ensure its continuous power supply. That is:

[0111] ;

[0112] ;

[0113] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv P represents the actual output power of the photovoltaic cell. bat This represents the actual output power of the energy storage battery.

[0114] Modes 1-3: Similar to Modes 1-2, the system is in a power transfer state, and the transmission power of each power conversion unit does not exceed the rated limit. The photovoltaic cells use MPPT control to achieve efficient utilization of distributed new energy, and the batteries perform charging and discharging operations within their safe operating range. Due to factors such as a fault in the AC distribution network 2 feeder, a transformer fault in the distribution area, and distribution network maintenance, AC port 2 is in an off-grid state. The DC distribution area and AC distribution network 1 transfer power to AC load 2 based on port power distribution to ensure its continuous power supply. That is:

[0115] ;

[0116] ;

[0117] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv P represents the actual output power of the photovoltaic cell. bat This represents the actual output power of the energy storage battery.

[0118] Modes 1-4: The system is in a power transfer state, and the transmission power of each power conversion unit does not exceed the rated limit. The photovoltaic cells use MPPT control to achieve efficient utilization of distributed new energy, and the batteries perform charging and discharging operations within their safe operating range. Due to faults in AC distribution network feeders 1 and 2, transformer faults in the distribution area, and distribution network maintenance, AC ports 1 and 2 are both in an off-grid state. The AC distribution area is disconnected from the DC side, and the SOP performs power transfer to the AC load based on the port power distribution. Existing:

[0119] ;

[0120] ;

[0121] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv P represents the actual output power of the photovoltaic cell. bat This represents the actual output power of the energy storage battery.

[0122] Mode 2-1: The system is in a power transfer state. The energy storage battery has reached its discharge threshold. To avoid the risk of over-discharge caused by continuous battery discharge, the energy storage battery module operates in standby mode, only capable of charging and not discharging. Due to factors such as a fault in the AC distribution network 1 feeder, a transformer fault in the distribution area, and distribution network maintenance, AC port 1 is in an off-grid state. The DC distribution area and AC distribution network 2 transfer power to AC load 1 based on port power distribution to ensure its continuous power supply. The photovoltaic module control strategy switches to MPPT control mode to maximize the utilization of renewable energy. At this time, we have:

[0123] ;

[0124] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv This represents the actual output power of the photovoltaic cell.

[0125] Mode 2-2: Similar to Mode 2-1, the system is in a power transfer state. The energy storage battery reaches its discharge threshold. To avoid the risk of over-discharge caused by continuous battery discharge, the energy storage battery module operates in standby mode, only capable of charging and not discharging. Due to factors such as a fault in the AC distribution network 2 feeder, a transformer fault in the distribution area, and distribution network maintenance, AC port 2 is in an off-grid state. The DC distribution area and AC distribution network 1 transfer power to AC load 2 based on port power distribution to ensure its continuous power supply. The photovoltaic module control strategy switches to MPPT control mode to maximize the utilization of renewable energy. At this time, we have:

[0126] ;

[0127] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv This represents the actual output power of the photovoltaic cell.

[0128] Mode 2-3: The system is in a power transfer state. The energy storage battery has reached its discharge threshold. To avoid the risk of over-discharge caused by continuous battery discharge, the energy storage battery module operates in standby mode, allowing only charging and preventing further discharge. Due to faults in AC distribution network feeders 1 and 2, transformer faults in the distribution area, and distribution network maintenance, AC ports 1 and 2 are both off-grid. The AC distribution area is disconnected from the DC side. The SOP performs power transfer to the AC load based on port power distribution. Existing:

[0129] ;

[0130] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv This represents the actual output power of the photovoltaic cell.

[0131] Mode 3-1: The system is in normal interconnection state, and the transmission power of each power conversion unit does not exceed the rated limit. The battery has reached its charging threshold. To avoid the risk of overcharging due to continuous charging, the battery module operates in standby mode and can only discharge. The photovoltaic cells switch to power-limiting control mode; load P... L1 With load P L2 Both are in a stable power supply state; power exchange is achieved between distribution networks 1 and 2 through converters VSC1 and VSC2 to realize load balancing of feeders 2, i.e.:

[0132] ;

[0133] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv P represents the actual output power of the photovoltaic cell. bat This represents the actual output power of the energy storage battery.

[0134] Mode 3-2: The system is in a power transfer state, and the transmission power of each power conversion unit does not exceed the rated limit. The battery has reached its charging threshold. To avoid the risk of overcharging due to continuous charging, the battery module operates in standby mode and can only discharge. Due to factors such as a fault in the AC distribution network 1 feeder, a transformer fault in the distribution area, and distribution network maintenance, AC port 1 is in an off-grid state. The DC distribution area and AC distribution network 2 transfer power to AC load 1 based on port power distribution. The photovoltaic cells switch to power limiting control mode; load P... L1 With load P L2 Both are under stable power supply; that is:

[0135] ;

[0136] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv P represents the actual output power of the photovoltaic cell. bat This represents the actual output power of the energy storage battery.

[0137] Mode 3-3: The system is in a power transfer state, and the transmission power of each power conversion unit does not exceed the rated limit. The battery has reached its charging threshold. To avoid the risk of overcharging due to continuous charging, the battery module operates in standby mode and can only discharge. Due to factors such as a fault in the AC distribution network 1 feeder, a transformer fault in the distribution area, and distribution network maintenance, AC port 2 is in an off-grid state. The DC distribution area and AC distribution network 1 transfer power to AC load 2 based on port power distribution. The photovoltaic cells switch to power limiting control mode; load P L1 With load P L2 Both are under stable power supply; that is:

[0138] ;

[0139] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv P represents the actual output power of the photovoltaic cell. bat This represents the actual output power of the energy storage battery.

[0140] Mode 3-4: The system is in a power transfer state, and the transmission power of each power conversion unit does not exceed the rated limit. The battery has reached the charging threshold. To avoid the risk of overcharging due to continuous battery charging, the battery module operates in standby mode and can only discharge. Due to faults in AC distribution network feeders 1 and 2, transformer faults in the distribution area, and distribution network maintenance, AC ports 1 and 2 are both off-grid. The AC distribution area is disconnected from the DC side. The SOP performs power flow transfer to the AC load based on the port power distribution; that is:

[0141] ;

[0142] In the formula, P ac1 For the output power of AC distribution network 1, P ac2 For the output power of AC distribution network 2, P L1 P is the power required by AC load 1. L2 P is the power required for AC load 2. vsc1 P represents the actual output power of inverter 1. vsc2 P represents the actual output power of inverter 2. pv P represents the actual output power of the photovoltaic cell. bat This represents the actual output power of the energy storage battery.

[0143] Step 103: Determine the current operating status of the multi-port flexible interconnection system based on the connection status of each AC port to the DC side and the feeder operating conditions.

[0144] It should be noted that step 102 introduces three operating modes (Mode 1, Mode 2, and Mode 3) based on the working status of the energy storage battery. In actual operation, the multi-port flexible interconnection system uses multiple feeders to achieve power support and fault transfer between different distribution networks. Therefore, this invention distinguishes three different operating states based on the AC distribution network fault conditions and the connection status of the AC and DC sides of the flexible interconnection system: normal interconnection state, power transfer state, and emergency state, wherein:

[0145] Normal interconnection status: All AC ports are connected to the DC side for operation;

[0146] It should be noted that the AC-side distribution network and the DC-side network are connected and operated through SOP. The network responds to dispatch instructions based on the surplus or deficit of active power on the AC and DC sides, absorbs distributed power sources, maintains power balance on both AC and DC sides, and achieves load balancing of feeders.

[0147] Power transfer status: At least one AC port is disconnected from the DC side due to fault or maintenance, and its original power supply load is transferred to the remaining normal ports through a flexible interconnection device;

[0148] It should be noted that, taking the N-1 fault in the system as an example, the load of the faulty feeder is flexibly switched to the normal feeder and the DC-side photovoltaic storage unit through SOP.

[0149] Emergency state: All AC ports are disconnected from the DC side, entering an islanded state. The DC side provides short-term emergency power to preset critical loads.

[0150] It should be noted that the AC-side distribution transformer area is disconnected from the DC side due to a fault and is in a completely isolated state. The important loads at the end of the AC feeder are supplied with short-term emergency power by the DC side. Energy storage provides partial power support for the important loads on the AC side while stabilizing the DC bus voltage.

[0151] Step 104: Based on the basic control model, combined with the basic working mode and operating status of photovoltaic-storage synergy, power coordination and voltage support control are performed to generate and output the actual power commands of each inverter, so as to realize the power coordination and voltage support of the multi-port flexible interconnection system.

[0152] In one embodiment, before performing power coordination and voltage support control in step 104, the system further includes: calculating the critical redundancy power of the multi-port flexible interconnection system, determining the operating status of the multi-port flexible interconnection system based on the critical redundancy power, and cutting off preset non-critical loads when the operating status is a deficit state.

[0153] Specifically, this invention defines P ry Critical redundancy power for multi-port flexible interconnect systems:

[0154] ;

[0155] In the formula, S T1 S T2 cosφ1 and cosφ2 represent the rated capacity of transformer 1, the rated capacity of transformer 2, the power factor of transformer 1, and the power factor of transformer 2, respectively. λ1 and λ2 represent the connection status of feeders 1 and 2, respectively. P L1 P is the power required for AC load 1. L2 The power required for AC load 2.

[0156] It should be noted that when P ry A value greater than zero indicates that the multi-port flexible interconnection system is operating in a redundant state; otherwise, it is operating in a deficient state. In this case, some non-critical loads should be disconnected, i.e., P should be used. LiZ Replace P Li This judgment condition applies to all working modes and will not be elaborated further.

[0157] It should be noted that step 104 determines the applicable target sub-mode from several coordination control sub-modes based on the combination of the basic working mode of photovoltaic-storage synergy and the current operating state of the multi-port flexible interconnection system; based on the power balance equation and basic control model corresponding to the target sub-mode, the actual power command of each inverter is generated and output to realize the power coordination and voltage support of the multi-port flexible interconnection system.

[0158] For example, when the basic working mode of photovoltaic-storage synergy is constant power charging mode and the system is in normal interconnection state, the target sub-mode can be set as the "energy storage priority charging - photovoltaic full consumption" coordinated control sub-mode. In this case, the reference power of the energy storage inverter in the power balance equation is its maximum allowable charging power, while the reference power of the photovoltaic inverter tracks the maximum output power in real time according to the light intensity, while ensuring that the DC bus voltage is stable near the rated value. If the basic working mode of photovoltaic-storage synergy switches to constant power discharge mode, and the system enters the power transfer state due to N-1 fault, the target sub-mode can be adjusted to the "energy storage emergency discharge - photovoltaic priority support for faulty feeders" coordinated control sub-mode. In this case, the power balance equation needs to prioritize the load demand of the faulty feeder, and the energy storage... The inverter outputs its maximum allowable discharge power. Besides meeting the load it connects to, the remaining output power of the photovoltaic inverter is used for power transfer. Simultaneously, the droop characteristic dynamically adjusts the power distribution across each port to maintain the AC and DC voltages within a safe range. When the basic photovoltaic-storage co-operation mode is float charging and the system is in an emergency state, the target sub-mode is a coordinated control sub-mode of "energy storage float charging to maintain voltage – photovoltaic on-demand support for important loads." In this power balance equation, the energy storage inverter only outputs a small amount of float charging current required to maintain the DC bus voltage stability. The photovoltaic inverter adjusts its output according to the real-time power demand of the important AC loads, ensuring continuous and reliable emergency power supply to the important loads while the energy storage SOC remains within a safe range.

[0159] This invention provides a power coordination and voltage support control method. By introducing DC-side voltage feedback to establish virtual inertia, it achieves voltage self-support and power balance control of the inverter. By introducing a photovoltaic-storage collaborative control strategy that considers the safe operating range of energy storage batteries and a power coordination control strategy for multi-port flexible interconnection systems, it achieves distributed flexible interconnection and adaptive power allocation, significantly improving the flexibility of power flow distribution and the overall energy utilization rate of the system. Simultaneously, the system can automatically rebalance power through frequency offset, thus maintaining voltage and frequency stability under light fluctuations or load disturbances. In summary, this invention significantly improves the stability, practicality, and economy of multi-port flexible interconnection power distribution systems. It thus solves the problems of insufficient power coordination capability, insufficient voltage support capability, and poor mode switching smoothness and reliability in existing technologies.

[0160] The above is a power coordination and voltage support control method provided in the embodiments of the present invention. The following is a power coordination and voltage support control system provided in the embodiments of the present invention.

[0161] Please see Figure 3 The power coordination and voltage support control system provided in this embodiment of the invention includes:

[0162] Unit 201 is used to establish the basic control model of the multi-port flexible interconnection system. The basic control model includes: a voltage control and power balance model based on DC voltage, a dynamic model of the inverter DC side based on virtual inertia, and a power regulation relationship based on droop characteristics.

[0163] The first design unit 202 is used to determine the current basic working mode of the multi-port flexible interconnection system based on the comparison between the real-time state of charge of the energy storage battery and the preset safe working range of the energy storage battery.

[0164] The second design unit 203 is used to determine the current operating status of the multi-port flexible interconnection system based on the connection status of each AC port to the DC side and the feeder operating conditions in the multi-port flexible interconnection system.

[0165] The control unit 204 is used to perform power coordination and voltage support control based on the basic control model and combined with the basic working mode and operating status of photovoltaic-storage collaboration, thereby generating and outputting the actual power commands of each inverter to realize power coordination and voltage support of the multi-port flexible interconnection system.

[0166] Furthermore, this embodiment of the invention also provides a power coordination and voltage support control device, the device including a processor and a memory:

[0167] The memory is used to store program code and transmit the program code to the processor;

[0168] The processor is used to execute the steps of the power coordination and voltage support control method as described in the above method embodiments, according to the instructions in the program code.

[0169] Furthermore, this embodiment of the invention also provides a computer-readable storage medium for storing program code for executing the power coordination and voltage support control method described in the above method embodiments.

[0170] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0171] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0172] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0173] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0174] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0175] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power coordination and voltage support control method, characterized in that, include: A basic control model for a multi-port flexible interconnection system is established. The basic control model includes: a voltage control and power balance model based on DC voltage, a dynamic model of the inverter DC side based on virtual inertia, and a power regulation relationship based on droop characteristics. Based on the comparison between the real-time state of charge of the energy storage battery and the preset safe operating range of the energy storage battery, the current basic working mode of photovoltaic-energy storage collaboration of the multi-port flexible interconnection system is determined. Based on the connection status of each AC port and DC side and the feeder operating condition in the multi-port flexible interconnection system, the current operating status of the multi-port flexible interconnection system is determined. Based on the aforementioned basic control model, and combined with the aforementioned photovoltaic-storage collaborative basic working mode and operating status, power coordination and voltage support control are performed to generate and output the actual power commands of each inverter, thereby realizing the power coordination and voltage support of the multi-port flexible interconnection system.

2. The power coordination and voltage support control method according to claim 1, characterized in that, The process of establishing the DC-side dynamic model of the inverter based on virtual inertia includes: An energy balance equation containing a virtual angular frequency and DC-side voltage is constructed for the i-th inverter. A virtual inertia parameter is introduced into the equation to characterize the inertial response characteristics of the inverter, so as to obtain the DC-side dynamic model of the inverter based on virtual inertia.

3. The power coordination and voltage support control method according to claim 2, characterized in that, The process of establishing the power regulation relationship based on droop characteristics includes: A droop relationship between the virtual angular frequency and active power is established, and based on the droop relationship and the small-signal linearization model of DC voltage, a reference power regulation law for adjusting photovoltaic cells and energy storage batteries is derived to obtain the power regulation relationship based on the droop characteristic.

4. The power coordination and voltage support control method according to claim 1, characterized in that, The preset safe operating range of the energy storage battery is between 80% and 20% of its real-time state of charge; the basic working mode of photovoltaic-energy storage collaboration includes: When the real-time state of charge is within the safe operating range, the photovoltaic system operates in maximum power point tracking mode, and the energy storage battery is charged and discharged on demand. When the real-time state of charge is lower than 20% of the real-time state of charge limit, the photovoltaic system operates in maximum power point tracking mode, and the energy storage battery is prohibited from discharging. When the real-time state of charge is higher than 80% of the upper limit of the real-time state of charge, the photovoltaic system switches to a power-limited operation mode, and the energy storage battery is prohibited from charging.

5. The power coordination and voltage support control method according to claim 4, characterized in that, The basic working mode of optical-storage collaboration is combined with the current operating state of the multi-port flexible interconnection system to form several coordinated control sub-modes; Each of the aforementioned coordinated control sub-modes corresponds to a preset power balance equation, which is used to determine the power distribution relationship between photovoltaics, energy storage batteries, inverters and AC distribution networks under preset real-time state of charge constraints and preset operating conditions.

6. The power coordination and voltage support control method according to claim 5, characterized in that, The current operating state of the determined multi-port flexible interconnection system includes one of the following three types: Normal interconnection status: All AC ports are connected to the DC side for operation; Power transfer status: At least one AC port is disconnected from the DC side due to fault or maintenance, and its original power supply load is transferred to the remaining normal ports through a flexible interconnection device; Emergency state: All AC ports are disconnected from the DC side and are in an islanded state. The DC side provides short-term emergency power supply to preset critical loads.

7. The power coordination and voltage support control method according to claim 1, characterized in that, The aforementioned power coordination and voltage support control also includes, prior to: Calculate the critical redundancy power of the multi-port flexible interconnection system, determine the operating status of the multi-port flexible interconnection system based on the critical redundancy power, and cut off the preset non-critical loads when the operating status is in a deficit state.

8. A power coordination and voltage support control system, characterized in that, include: A modeling unit is established to build the basic control model of a multi-port flexible interconnection system. The basic control model includes: a voltage control and power balance model based on DC voltage, a dynamic model of the inverter DC side based on virtual inertia, and a power regulation relationship based on droop characteristics. The first design unit is used to determine the current basic working mode of the multi-port flexible interconnection system for photovoltaic-storage collaboration based on the comparison between the real-time state of charge of the energy storage battery and the preset safe working range of the energy storage battery. The second design unit is used to determine the current operating status of the multi-port flexible interconnection system based on the connection status of each AC port to the DC side and the feeder operating conditions in the multi-port flexible interconnection system. The control unit is used to perform power coordination and voltage support control based on the basic control model, combined with the basic working mode of photovoltaic-storage collaboration and the operating state, thereby generating and outputting the actual power commands of each inverter to realize the power coordination and voltage support of the multi-port flexible interconnection system.

9. A power coordination and voltage support control device, characterized in that, The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the power coordination and voltage support control method according to any one of claims 1-7 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program code for executing the power coordination and voltage support control method according to any one of claims 1-7.

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