A method for power sharing of multiple marine diesel generators in series

Abstract

The application discloses a kind of power equalization methods of marine diesel generator multiple machines in series, first by main controller acquisition each unit circuit breaker state, unit voltage and current parameters, using series logic algorithm identification networking topology and construct networking admittance matrix, then the equivalent impedance and dynamic droop coefficient of each unit are calculated, the dynamic characteristics of power distribution are optimized, using mutual admittance compensation term offsets the coupling interference between series unit, calculate voltage deviation correction amount to eliminate the risk of reverse power caused by single machine into motor state, finally the reference power command and voltage compensation value are input PID or integral adjustment model of local controller to realize power accurate regulation.The application solves the problem of voltage natural imbalance under current rigid constraint in series circuit, realizes the automatic equalization of multiple unit terminal voltage and power reasonable distribution, enhances the reliability, dynamic response capability and system expansibility of ship high-voltage direct-current power supply system.

Description

Technical Field

[0001] This invention belongs to the field of power electronic equipment and its control technology, and specifically relates to a power sharing method for multiple marine diesel generators connected in series. Background Technology

[0002] Currently, in ship power plant systems, power distribution and voltage stability of multiple diesel generators are core requirements for ensuring reliable power supply, and related technologies mainly focus on parallel operation systems. However, in certain specific high-voltage DC application scenarios, in order to reduce transmission losses or meet special load requirements, it is necessary to construct a high-voltage DC power supply.

[0003] While this can be achieved using high-power IGBTs or multi-stage Buck-Boost cascade structures, it also increases system complexity and cost. Directly connecting multiple diesel generator sets in series is a straightforward way to achieve high voltage, but it still faces many challenges in practical engineering applications and has not yet been widely adopted.

[0004] The main reasons are as follows: the current is the same throughout the series circuit, but the internal resistance, mechanical characteristics, and dynamic response of each unit are different, which makes it impossible for the terminal voltages of each unit to be naturally balanced. The unit with higher voltage will bear too much power or even be overloaded, while the unit with lower voltage may enter motor mode, generating destructive reverse power flow, leading to system collapse.

[0005] Existing diesel generator control strategies are mainly designed for parallel operation or pure electric motor systems, and lack dedicated voltage balancing and power distribution control methods for multiple diesel generator sets operating in series. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for power sharing in a series connection of multiple marine diesel generators.

[0007] The technical solution adopted by this invention to solve its technical problem is: a power sharing method for multiple marine diesel generators connected in series, based on a control system composed of a main controller, a droop control unit, a voltage compensation unit, and a local controller. The main controller is composed of a data acquisition unit, a topology diagnostic unit, and a network matching unit connected in sequence; including the following steps:

[0008] S1, the acquisition unit acquires the terminal voltage and current parameters of the currently operating diesel generator and the circuit breaker status signals of each unit in real time, and transmits them to the topology diagnostic unit;

[0009] S2, the topology diagnostic unit determines the series operation status of the diesel generator through a series logic algorithm based on the circuit breaker switch status signal of the unit transmitted by the acquisition unit. Based on this, it constructs an n×n network admittance matrix Y containing self-admittance and mutual admittance elements, and finally inputs the matrix into the network matching unit.

[0010] S3, the network matching unit calculates the equivalent impedance and dynamic droop coefficient based on the network admittance matrix Y, and transmits the results to the droop control unit and the voltage compensation unit respectively. The droop control unit determines the power distribution ratio among multiple units through the dynamic droop coefficient.

[0011] S4, the local controller integrates the reference power command and the deviation correction value output by the voltage compensation unit to calculate the control command of the diesel generator set. The local controller of each unit receives the control value and adjusts the governor of the diesel engine and the excitation system of the generator accordingly, thereby completing the power and voltage control of a single unit and realizing the power distribution of the series diesel generator sets.

[0012] Furthermore, in step S2, the n×n network admittance matrix ,in , where n is the total number of generating units; Z i The equivalent impedance of unit i ( R i X is a resistor. i (for reactance) Indicates the branch switch status (0 open, 1 closed) connecting units i and j; matrix Y satisfies that the row sum is zero. ).

[0013] Furthermore, the serial logic algorithm described in step S2 includes the following steps:

[0014] First, the diesel generator circuit breakers are classified into branch circuit breakers, main bus tie circuit breakers, and auxiliary bus tie circuit breakers according to their functional attributes. Among them, branch circuit breakers refer to the switch nodes that directly connect each diesel generator to the busbar; main bus tie circuit breakers and auxiliary bus tie circuit breakers refer to the horizontal switches used to connect different busbar sections under parallel operation conditions.

[0015] Then, read the status of each circuit breaker. If both the main and auxiliary bus tie circuit breakers are open, each bus section is isolated. If the branch circuit breakers are closed in sequence, each generator unit will be connected end to end, forming a chain-like series circuit without branches.

[0016] Finally, based on graph theory topology analysis, an adjacency matrix of the marine diesel generator set network topology is constructed to detect the connectivity status of each generator set node in the network: if any two or more diesel generator sets are detected to form a chain-like or branchless chain-like connection path through a closed branch circuit breaker, and both the main bus tie circuit breaker and the auxiliary bus tie circuit breaker are in an open state, then the system is determined to be in series operation mode, and the off-diagonal and diagonal elements of the n×n network admittance matrix Y are dynamically updated according to the position of the closed branch circuit breaker; if the main bus tie circuit breaker or the auxiliary bus tie circuit breaker is detected to be in a closed state, then the system is determined to be in parallel operation mode, and the parallel control strategy is automatically switched.

[0017] Furthermore, the dynamic droop coefficient in step S3 can be adaptively updated based on the power value of the previous sampling period, and it is defined as follows: ,in Let be the reference droop coefficient for unit i. Let be the self-admittance element of unit i in the admittance matrix, and ≠0, This indicates the coupling polarity (+1 or -1) between the generator unit and the system. The maximum active power of unit i. Let be the actual active power of unit i collected in the (k-1)th cycle. The dead zone threshold is set to 1% to 5% of the maximum active power of unit i. It is used to prevent the denominator from being zero and to ensure system stability and suppress regulation oscillations under low power conditions.

[0018] Furthermore, in step S3, the power allocation adopts an incremental control strategy based on the deviation, defined as follows: Assuming that in a series system of multiple diesel generators, the frequency deviation of all units is the same in steady state ( Furthermore, power distribution is only related to voltage deviation. If related, then the frequency deviation is defined as The formula can then be rewritten as follows: Assume the system has n generator units, and the total load power is... Substituting into the above formula, we can obtain This allows us to obtain the power of each unit: ,in ; The self-admittance symbol of the admittance matrix Substituting into the above formula, considering the relationship between the combined frequency deviation and voltage deviation, the power allocation command for each unit is determined. It can be deduced as ,in The target power of unit i in the k-th period is calculated based on the admittance matrix. Let be the actual active power of unit i collected in the k-th cycle. This is the dead zone threshold.

[0019] Furthermore, the voltage compensation equation of the voltage compensation unit in step S3 is defined in the per-unit system as follows: ,in and These are the voltage reference values ​​for unit i on the d-axis and q-axis, respectively. and They are respectively mutual admittance Y ij The real and imaginary parts, namely the inter-unit mutual admittance coupling compensation term. and These are the voltage-power sensitivity coefficients of unit i on the d-axis and q-axis, respectively, which can be calibrated offline using the unit's transient reactance parameters; The dimensionless voltage compensation adjustment gain of unit i; the trigger condition of the voltage compensation unit is: when the voltage amplitude of any adjacent unit j satisfies At that time, the mutual admittance compensation term is activated, wherein This is the preset voltage fluctuation threshold.

[0020] Furthermore, in step S4, the control quantity is divided into two parts: power distribution control and voltage compensation control. The local controller controls the control quantity according to the local sampling period. Independent operation involves incorporating the control quantity into a digital PID controller or discrete integral circuit to obtain the control quantity expression. ,in , These are the integration coefficients, ensuring that the system converges to the target value. , Set target values ​​for the power and voltage of unit i, where n is the current sampling time and n-1 is the previous sampling time. , This represents the actual power and voltage during the m-th sampling period.

[0021] The beneficial effects of the invention are:

[0022] 1. This invention achieves robust output of high-voltage DC power by directly connecting multiple diesel generator sets in series. Compared to traditional high-power multi-stage converters (such as Buck-Boost cascaded) or ultra-high-power IGBT solutions, this invention eliminates the need for additional DC / DC converters and complex power conversion links, significantly reducing system equipment costs, size, and transmission losses, and improving the utilization rate of ship engine room space.

[0023] 2. This invention addresses the problem of voltage imbalance caused by the uniform current of each unit in a series circuit but differences in internal resistance and mechanical response, by introducing a dynamic droop control loop for voltage deviation. By adaptively adjusting the power setpoint of each unit, automatic voltage balancing is achieved. This fundamentally prevents the risk of insulation breakdown or the unit entering motor operation mode (generating destructive circulating current) due to voltage unevenness.

[0024] 3. This invention introduces a power compensation stage based on the mutual admittance matrix. This stage can calculate and offset the coupling effect of voltage fluctuations from adjacent units on the unit's power in real time. This feedforward compensation mechanism enhances the system's damping characteristics, effectively suppresses the risk of global oscillation caused by sudden load changes in a single unit under series operation, and significantly shortens the dynamic response time for the system to reach steady state.

[0025] 4. This invention achieves automated identification of complex circuit breaker combination states by constructing a network admittance matrix and a series logic algorithm. It eliminates the traditional hard-wired control link, reducing the physical complexity of the control system. When increasing or decreasing the number of series units, only the admittance matrix parameters need to be updated to complete the adaptation, improving engineering scalability and system reliability.

[0026] 5. This invention overcomes the problem of natural voltage imbalance under the rigid current constraint of series circuits, and realizes voltage balance and power distribution of series units through digital intelligent control, filling a technological gap. Attached Figure Description

[0027] Figure 1 This is a topology diagram of the control system of this invention;

[0028] Figure 2 This is a flowchart of the power control method of the present invention;

[0029] Figures 3-5 This is a comparison diagram of the terminal voltage response of three units under load sudden change according to the present invention;

[0030] Figures 6-8 This is a comparison diagram of the circulating current of three units under sudden load changes according to the present invention.

[0031] The labels in the attached figures are as follows: 1—Main controller, 11—Acquisition unit, 12—Topology diagnostic unit, 13—Network matching unit, 2—Droop control unit, 3—Voltage compensation unit, 4—Local controller. Detailed Implementation

[0032] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0033] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

[0034] Example 1

[0035] This invention discloses a power-sharing method for multiple marine diesel generators connected in series, the method being based on... Figure 1 The control system shown is composed of a main controller 1, a droop control unit 2, a voltage compensation unit 3, and a local controller 4. Specifically, the main controller 1 is composed of a data acquisition unit 11, a topology diagnostic unit 12, and a network matching unit 13 connected in sequence.

[0036] like Figure 1 As shown, the top layer is the perception and modeling layer, which mainly includes state matrix acquisition and admittance matrix reconstruction; the middle layer is the dual-path parallel computing layer, which processes droop power distribution and voltage decoupling compensation in parallel; and the bottom layer is the execution layer, which drives the diesel engine governor and excitation system through the local controller.

[0037] Reference Figure 2 As shown, the specific control method in this embodiment includes the following steps.

[0038] S1. During system operation, the acquisition unit 11 acquires the electrical parameters (including terminal voltage and current) of all operating diesel generators in the current network and the switching status signals of each unit's circuit breaker in real time, and transmits these real-time data to the topology diagnostic unit 12 at high speed.

[0039] S2, after receiving the circuit breaker switch status signals of each generator set, the topology diagnostic unit 12 runs a series logic algorithm to determine the network topology of the entire diesel generator set.

[0040] Specifically, based on graph theory topology analysis, an adjacency matrix of the marine diesel generator set network topology is constructed to detect the connectivity status of each generator set node within the network. If any two or more diesel generator sets are detected to form a chain-like or branchless chain-like connection path through a closed branch circuit breaker, and both the main bus tie circuit breaker and the auxiliary bus tie circuit breaker are in an open state, then the system is determined to be in series operation mode, and the off-diagonal and diagonal elements of the n×n network admittance matrix Y are dynamically updated according to the position of the closed branch circuit breaker. If the main bus tie circuit breaker or the auxiliary bus tie circuit breaker is detected to be in a closed state, then the system is determined to be in parallel operation mode, and the parallel control strategy is automatically switched. Based on the determination of series operation mode, the topology diagnostic unit 12 constructs the corresponding n×n network admittance matrix Y and inputs it into the network matcher 13. The specific definition and element calculation rules of matrix Y are as follows: n×n network admittance matrix off-diagonal elements (When i≠j), diagonal elements (When i = j); where n in the matrix is ​​the total number of units, Z i The equivalent impedance of unit i ( R i X is a resistor. i (For reactance), switch state variables Indicates the branch switch status (0 open, 1 closed) connecting units i and j; the matrix satisfies Kirchhoff's current law constraint that the row sum is zero: matrix Y satisfies the row sum being zero ( ).

[0041] As a specific embodiment, the serial logic algorithm includes the following steps.

[0042] First, the diesel generator circuit breakers are classified according to their functional attributes into branch circuit breakers, main bus tie circuit breakers, and auxiliary bus tie circuit breakers.

[0043] Then, read the status of each circuit breaker: if both the main bus tie circuit breaker and the auxiliary bus tie circuit breaker are open, each bus section is isolated. If the branch circuit breakers are closed in sequence, each generator unit will be connected end to end, forming a chain-like series circuit without branches.

[0044] Finally, based on graph theory topology analysis, an adjacency matrix of the marine diesel generator set network topology is constructed to detect the connectivity status of each generator set node in the network: if any two or more diesel generator sets are detected to form a chain or unbranched chain connection path through a branch circuit breaker in a closed state, and both the main bus tie circuit breaker and the auxiliary bus tie circuit breaker are in an open state, then the system is determined to be in series operation mode, and the off-diagonal and diagonal elements of the n×n network admittance matrix Y are dynamically updated according to the position of the branch circuit breaker in a closed state; if the main bus tie circuit breaker or the auxiliary bus tie circuit breaker is detected to be in a closed state, then the system is determined to be in parallel operation mode, and the parallel control strategy is automatically switched.

[0045] S3, the network matching unit 13 calculates the equivalent impedance of each unit based on the input admittance matrix Y. With dynamic droop coefficient The results are then transmitted to the droop control unit 2 and the voltage compensation unit 3, respectively, as follows.

[0046] First, the droop control unit 2 distributes steady-state power using a dynamic droop coefficient. In a series system, the power of unit i is affected by the voltage of other units j. Through mutual admittance compensation of coupling effects, the voltage compensation unit 3 analyzes the coupling effects between units and calculates the voltage deviation correction. When a sudden change in the load of unit j causes a voltage fluctuation, the feedforward compensation of mutual admittance in the network admittance matrix Y enables the control command of unit i to predict and offset the risk of reverse power flow caused by the fluctuation, thereby achieving independent and precise adjustment of the power of each node.

[0047] Power distribution employs an incremental control strategy based on deviation, defined as follows: Assuming that in a series system of multiple diesel generators, the frequency deviation of all units is the same in steady state ( Furthermore, power distribution is only related to voltage deviation. If related, then the frequency deviation is defined as The formula can then be rewritten as follows: Assume the system has n generator units, and the total load power is... Substituting into the above formula, we can obtain This allows us to obtain the power of each unit: ,in .

[0048] The dynamic sagging coefficient is defined as follows: Based on the relationship between the combined frequency deviation and voltage deviation, the power allocation commands for each unit are determined. This can be deduced as: ,in The target power of unit i in the k-th period is calculated based on the admittance matrix. Let be the actual active power of unit i collected in the k-th cycle. This is the dead zone threshold.

[0049] The dynamic droop coefficient in step S3 can be adaptively updated based on the power value of the previous sampling period, and it is defined as follows: ,in Let be the reference droop coefficient for unit i. Let be the self-admittance element of unit i in the admittance matrix, and ≠0, This indicates the coupling polarity (+1 or -1) between the generator unit and the system. The maximum active power of unit i. Let be the actual active power of unit i collected in the (k-1)th cycle. The dead zone threshold is set to 1% to 5% of the maximum active power of unit i. It is used to prevent the denominator from being zero and to ensure system stability and suppress regulation oscillations under low power conditions.

[0050] Then, in the series system, the terminal voltages of each unit are coupled to each other, and the voltage compensation unit 3 calculates the voltage deviation correction amount for this coupling effect.

[0051] The voltage compensation equation for voltage compensation unit 3 is defined in the per-unit system as follows: In the formula and These are the voltage reference values ​​for unit i on the d-axis and q-axis, respectively. and They are respectively mutual admittance Y ij The real and imaginary parts, namely the inter-unit mutual admittance coupling compensation term. and These are the voltage-power sensitivity coefficients of unit i on the d-axis and q-axis, respectively, which can be calibrated offline using the unit's transient reactance parameters; This is the dimensionless voltage compensation adjustment gain for unit i. The trigger condition for the compensation unit is: when the voltage amplitude of any adjacent unit j satisfies... At that time, the mutual admittance compensation term is activated, wherein This is a preset voltage fluctuation threshold. The system determines when the voltage of adjacent units... When a voltage deviation occurs, this compensation mechanism is triggered to counteract the interference of voltage fluctuations from other units on the power of this unit.

[0052] The and Although it is a transient calibration, in actual system operation, when the topology diagnostic unit 12 detects a change in the number of units or the network topology, the voltage compensation unit 3 will automatically adjust the feedforward compensation term according to the real-time updated admittance matrix Y. and By adjusting the weight values, the sensitivity coefficient failure caused by topological changes can be avoided.

[0053] Furthermore, to avoid the unit terminal voltage from falling within a preset voltage fluctuation threshold... When minute fluctuations occur at the edge, the mutual admittance compensation term is frequently started and stopped. The triggering condition of the voltage compensation unit 3 incorporates hysteresis comparison logic or a time confirmation mechanism. For example, when Furthermore, mutual admittance compensation is only initiated when this state persists for more than a set time window (e.g., 50ms); similarly, when the voltage difference drops below... The compensation process will only exit when δ is the preset hysteresis.

[0054] In a series system, the power of unit i is affected by the voltage of other units j. Through mutual admittance compensation of coupling effect, voltage compensation unit 3 analyzes the coupling effect between units and calculates the voltage deviation correction. When the load of unit j changes suddenly, causing the terminal voltage to fluctuate, through the feedforward compensation of mutual admittance in the network admittance matrix Y, the control command of unit i can predict and offset the risk of reverse power flow caused by the fluctuation, thereby realizing independent and precise adjustment of the power of each node.

[0055] S4, the local controller 4 integrates the reference power command and the deviation correction value output by the voltage compensation unit 3 to calculate the control command for the diesel generator set. The calculated power command and voltage compensation reference value are sent to the local controller 4 of each generator set. The local controller 4 of each generator set receives the control values ​​and incorporates the power distribution control and voltage compensation control into the PID regulator (or integral term) to obtain the final control expression. .

[0056] Furthermore, based on the control reference values ​​calculated above, the local controller 4 adjusts the fuel rack position of the diesel engine governor and the excitation current of the generator's automatic voltage regulator (AVR) in real time and accurately, thereby completing the decoupled control of the power and terminal voltage of a single unit.

[0057] It should be noted that, in this embodiment, the dead zone threshold... The value range is set to 1% to 5% of the maximum active power of unit i. This range is determined based on the actual operating characteristics of the ship's high-voltage DC power supply system; if If the value is less than 1%, the system is overly sensitive to small power fluctuations, easily leading to frequent changes in the droop coefficient, causing mechanical wear of the diesel engine governor and high-frequency oscillations in the system; if... A value greater than 5% will result in a blind spot in the control system under low-power unbalanced conditions, making it unable to perform power equalization in a timely manner, thus worsening the voltage balancing effect under light loads. Therefore, the optimal balance condition can be achieved in the range of 1%-5%.

[0058] Example 2

[0059] This embodiment uses the Matlab simulation platform to construct a digital simulation model of a multi-machine series power control system for marine diesel generators, and performs comparative verification.

[0060] Three marine diesel generator sets of the same model (labeled DG1, DG2, and DG3 respectively) are set to operate in series. The specific parameters are shown in the table below.

[0061] .

[0062] In Embodiment 2, the simulation process is as follows.

[0063] Reference Figures 3 to 8 As shown, during the stable operation phase of the system (e.g., at t=2.5s), the steady-state output power (P1, P2, P3) and terminal voltage (V1, V2, V3) of the three units are extracted from the simulation results of the traditional method and the method of the present invention, respectively.

[0064] In the traditional method, the calculated average power is Pavg≈250kW; the power deviation rates of each unit are: δP1≈6.0%, δP2≈8.5%, δP3≈5.0%, with a maximum power deviation of 8.5%; the voltage values ​​of each unit are: V1=402.1V, V2=395.2V, V3=404.3V, with a maximum voltage deviation of 5.2V.

[0065] In the method of this invention, the calculated average power is Pavg≈250kW; the power deviation rate of each unit is less than 1.2%; the voltage values ​​of each unit are: V1=400.5V, V2=399.8V, V3=400.2V; the maximum voltage deviation is 0.8V.

[0066] Analysis revealed that, due to the inherent equivalent impedance differences (Z1, Z2, and Z3 are different) in series-connected units, the voltage and power borne by each unit will inevitably be uneven under the control of a fixed droop coefficient, with the unit power deviation reaching 8.5% and the voltage deviation reaching 5.2V.

[0067] The method of this invention uses a dynamic droop coefficient The impedance difference is adaptively compensated, and the coupling interference is canceled by the mutual admittance compensation term. This enables the control system to overcome the differences in hardware parameters and dynamically adjust the control commands of each unit, so that the power and voltage converge towards the equilibrium point, achieving an even distribution effect (unit power deviation <1.2%, voltage deviation <0.8V).

[0068] The power sharing method provided by the embodiments of the present invention fully considers the actual series application scenario. Without adding additional DC / DC conversion hardware, it automatically smooths out the voltage unevenness and circulating current risks caused by the series connection of each unit by using digital logic and dynamic voltage equalization strategy, thus ensuring the stability and safety of the high-voltage DC power supply system.

[0069] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for power sharing in a multi-unit series connection of marine diesel generators, characterized in that: The control system is based on a main controller (1), a droop control unit (2), a voltage compensation unit (3), and a local controller (4). The main controller (1) is composed of a data acquisition unit (11), a topology diagnostic unit (12), and a network matching unit (13) connected in sequence. The system includes the following steps: S1, the acquisition unit (11) acquires the terminal voltage and current parameters of the currently running diesel generator and the circuit breaker status signals of each unit in real time, and transmits them to the topology diagnostic unit (12). S2, the topology diagnostic unit (12) determines the series operation status of the diesel generator through the series logic algorithm, constructs an n×n network admittance matrix Y containing self-admittance and mutual admittance elements, and inputs it into the network matcher (13). S3, the network matching unit (13) calculates the equivalent impedance and dynamic droop coefficient based on the network admittance matrix Y, and transmits them to the droop control unit (2) and the voltage compensation unit (3) respectively. The droop control unit (2) determines the power distribution ratio among multiple units through the dynamic droop coefficient. S4, the local controller (4) calculates the control command of the diesel generator set based on the deviation correction value output by the reference power command and the voltage compensation unit (3). The local controller (4) adjusts the governor of the diesel engine and the excitation system of the generator to complete the power and voltage control of a single unit and realize the power distribution of the series diesel generator set.

2. The power sharing method for multiple marine diesel generators connected in series according to claim 1, characterized in that, In step S2, the n×n network admittance matrix ,in n is the total number of units, Z i Let be the equivalent impedance of unit i. R i X is a resistor. i Reactance, switch state variable This represents the branch switch status connecting units i and j, where 0 indicates open and 1 indicates closed. Matrix Y satisfies the condition that the row sum is zero. .

3. The power sharing method for multiple marine diesel generators connected in series according to claim 2, characterized in that, The concatenated logic algorithm in step S2 includes the following steps: First, the diesel generator circuit breaker is classified into branch circuit breaker, main bus tie circuit breaker and auxiliary bus tie circuit breaker according to its functional attributes. Then, read the status of each circuit breaker: if the main bus tie circuit breaker and the auxiliary bus tie circuit breaker are both open, each bus section is isolated. If the branch circuit breakers are closed in sequence, each generator unit will be connected end to end to form a chain-type series circuit without branches. Finally, based on graph theory topology analysis, an adjacency matrix of the marine diesel generator set network topology is constructed, and the connectivity status of each generator set node within the network is detected: If any two or more diesel generator sets are detected to form a chain or unbranched chain connection path through a branch circuit breaker in a closed state, and both the main bus tie circuit breaker and the auxiliary bus tie circuit breaker are in an open state, then the system is determined to be in series operation mode, and the off-diagonal and diagonal elements of the n×n network admittance matrix Y are dynamically updated according to the position of the branch circuit breaker in a closed state. If the main bus tie circuit breaker or the auxiliary bus tie circuit breaker is detected to be in a closed state, the system is determined to be in parallel operation mode and automatically switches to the parallel control strategy.

4. A power-sharing method for multiple marine diesel generators connected in series according to claim 1, 2, or 3, characterized in that, The dynamic droop coefficient in step S3 ,in Let be the reference droop coefficient for unit i. Let be the self-admittance element of unit i in the admittance matrix, and ≠0, Indicates the coupling polarity between the generator unit and the system. The maximum active power of unit i. Let be the actual active power of unit i collected in the (k-1)th cycle. This is the dead zone threshold.

5. The power sharing method for multiple marine diesel generators connected in series according to claim 4, characterized in that, In step S3, based on the incremental control strategy of the deviation, the power allocation formula is defined as follows: The frequency deviation is defined as The formula is: Let the total load power of the system's n generating units be... Substituting into the above formula, we can obtain This allows us to obtain the power of each unit. ,in ,; The self-admittance symbol of the admittance matrix Substituting into the above formula, considering the relationship between the combined frequency deviation and voltage deviation, the power allocation command for each unit is determined. ,in The target power of unit i in the k-th period is calculated based on the admittance matrix. Let be the actual active power of unit i collected in the k-th cycle. This is the dead zone threshold.

6. The power sharing method for multiple marine diesel generators connected in series according to claim 5, characterized in that, The voltage compensation equation of the voltage compensation unit (3) in step S3 is defined as follows in the per-unit system: ,in and These are the voltage reference values ​​for unit i on the d-axis and q-axis, respectively. and They are respectively mutual admittance Y ij The real and imaginary parts, and These are the voltage-power sensitivity coefficients of unit i on the d-axis and q-axis, respectively. The dimensionless voltage compensation adjustment gain of unit i; the triggering condition of the voltage compensation unit (3) is: when the voltage amplitude of any adjacent unit j satisfies At that time, the mutual admittance compensation term is activated, wherein This is the preset voltage fluctuation threshold.

7. A power sharing method for multiple marine diesel generators connected in series according to claim 1, 2, or 3, characterized in that, The control quantities in step S4 are divided into power distribution control and voltage compensation control. The local controller (4) controls the control quantities according to the local sampling period. Independent operation, the control quantity is obtained by introducing the control quantity into the digital PID regulator or discrete integral element. ,in , The integral coefficient is... , Set target values ​​for the power and voltage of unit i, where n is the current sampling time and n-1 is the previous sampling time. , This represents the actual power and voltage during the m-th sampling period.

Images