An emergency power supply system of urban power distribution network with diesel generator and energy storage converter in parallel and a control method thereof

Abstract

The application discloses an urban power distribution network emergency power supply system with diesel generators and energy storage converters in parallel, wherein a power distribution network is connected with a public connection point through a power distribution network grid-connected switch; a load is directly connected with the public connection point; a diesel generator is connected with the public connection point through a series-connected diesel generator grid-connected switch; an energy storage device is connected with one end of a double-ended DC / DC voltage source type converter; the other end of the double-ended DC / DC voltage source type converter is connected with a direct current end of a double-ended DC / AC voltage source type converter; an alternating current end of the double-ended DC / AC voltage source type converter is connected with the public connection point through a filter module; and a direct current side capacitor is connected between an input positive pole and an input negative pole of the direct current end of the double-ended DC / AC voltage source type converter. The application further discloses a control method of the urban power distribution network emergency power supply system with the diesel generators and the energy storage converters in parallel. The application not only realizes emergency power supply of the power distribution network, but also has higher reliability and better accuracy.

Description

Technical Field

[0001] This invention belongs to the field of electrical automation, specifically relating to an emergency power supply system for urban power distribution networks and its control method, in which a diesel generator and an energy storage converter are connected in parallel. Background Technology

[0002] With economic and technological development and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and daily life, bringing endless convenience. Therefore, ensuring a stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] Currently, power distribution networks are susceptible to power outages due to natural disasters and equipment failures. Therefore, emergency power supply systems have become core infrastructure for ensuring power continuity. Diesel generators offer stable power supply and large capacity, while energy storage systems provide rapid response and the ability to smooth power fluctuations. Consequently, emergency power supply solutions combining these two technologies have gradually become the mainstream solution for power distribution network emergency power supply.

[0004] However, current emergency power supply systems for distribution networks primarily employ a "diesel generator + energy storage converter + PCC point" topology. In this scheme, the energy storage converter, equipped with VSG control, achieves grid-connected / islanded switching. The diesel generator serves as a backup power source, starting when energy storage capacity is insufficient. The converter is connected to the system via RLC filtering, and the DC-side voltage is regulated by a DC / DC converter. While this approach provides basic emergency power supply, mode switching is often manually triggered or based on simple thresholds. Furthermore, power regulation relies solely on constant power or load tracking modes, and there is no dynamic coordination mechanism for power distribution between the diesel generator and the converter. Consequently, the reliability and accuracy of existing emergency power supply systems and their control schemes are relatively poor. Summary of the Invention

[0005] One of the objectives of this invention is to provide an emergency power supply system for urban power distribution networks that connects a diesel generator and an energy storage converter in parallel, offering high reliability and accuracy.

[0006] The second objective of this invention is to provide a control method for an urban power distribution network emergency power supply system in which the diesel generator and the energy storage converter are connected in parallel.

[0007] The urban power distribution network emergency power supply system provided by this invention, which connects a diesel generator and an energy storage converter in parallel, includes a diesel generator and an energy storage device, as well as a diesel generator grid-connection switch, a dual-terminal DC / DC voltage source converter, a DC-side capacitor, a dual-terminal DC / AC voltage source converter, and a filter module. The power distribution network is connected to a point of common coupling (PCC) via the grid-connection switch. The load is directly connected to the PCC. The diesel generator is connected to the PCC via a series-connected diesel generator grid-connection switch. The energy storage device is connected to one end of the dual-terminal DC / DC voltage source converter, and the other end of the dual-terminal DC / DC voltage source converter is connected to the DC terminal of the dual-terminal DC / AC voltage source converter. The AC terminal of the dual-terminal DC / AC voltage source converter is connected to the PCC via the filter module. The DC-side capacitor is connected in parallel between the positive and negative input terminals of the DC terminal of the dual-terminal DC / AC voltage source converter.

[0008] The dual-terminal DC / DC voltage source converter adopts a constant DC bus voltage control scheme to provide stable DC voltage support for the DC terminal of the dual-terminal DC / AC voltage source converter; the dual-terminal DC / AC voltage source converter can operate in grid-connected or islanded mode, and adopts a virtual synchronous generator control scheme.

[0009] The filtering module is an RLC filtering module.

[0010] The present invention also provides a control method for an urban power distribution network emergency power supply system in which the diesel generator and the energy storage converter are connected in parallel, comprising the following steps:

[0011] The control method described is a control method for a dual-terminal DC / AC voltage source converter;

[0012] The operating modes of dual-terminal DC / AC voltage source converters include grid-connected operation mode, islanded independent power supply mode, islanded collaborative power supply mode, and islanded long-term operation mode;

[0013] Grid-connected operation mode: When the voltage at the point of common coupling is higher than the set value, the grid-connected switch of the distribution network is closed, and the grid-connected switch of the diesel generator is opened; the dual-terminal DC / AC voltage source converter is in constant power control mode and outputs rated power; at this time, the emergency power supply system of the distribution network and the distribution network operate in parallel and jointly supply power to the load;

[0014] Isolated power supply mode: When the grid connection switch of the distribution network is open, the voltage of the common connection point is lower than the set value, and the rated power of the dual-terminal DC / AC voltage source converter is greater than the load power, the grid connection switch of the diesel generator is open, the dual-terminal DC / AC voltage source converter is in load tracking mode, and outputs according to the load power; at this time, the energy storage device supplies power to the load independently.

[0015] Islanded Cooperative Power Supply Mode: When the grid connection switch of the distribution network is open, the voltage at the point of common coupling is lower than the set value, and the rated power of the dual-terminal DC / AC voltage source converter is less than the load power, the grid connection switch of the diesel generator is closed, and the diesel generator is connected to the point of common coupling. The diesel generator and the dual-terminal DC / AC voltage source converter distribute the output power according to their own capacity to ensure that the sum of the output power of the diesel generator and the output power of the energy storage device meets the load requirements. At this time, the diesel generator and the energy storage device work together to supply power to the load.

[0016] Islanded long-term operation mode: When the dual-terminal DC / AC voltage source converter is in islanded independent power supply mode or islanded collaborative power supply mode, and the remaining capacity of the energy storage device reaches the set lower limit, the grid connection switch of the diesel generator is closed, and the diesel generator supplies power to the load; the dual-terminal DC / AC voltage source converter only outputs the minimum set power and keeps the output constant.

[0017] The voltage setting at the point of common coupling is 0.9 per unit.

[0018] The control process of a two-terminal DC / AC voltage source converter includes the following steps:

[0019] Acquire the output voltage, output current, and common coupling point voltage data of the dual-terminal DC / AC voltage source converter;

[0020] Based on the obtained output voltage of the dual-terminal DC / AC voltage source converter and output current ,go through Decomposition yields the d-axis voltage. q-axis voltage d-axis current and q-axis current The output active power of the dual-terminal DC / AC voltage source converter was calculated. for The output reactive power of the dual-terminal DC / AC voltage source converter was calculated. for ;

[0021] If the dual-terminal DC / AC voltage source converter operates in grid-connected mode, the rated power output of the dual-terminal DC / AC voltage source converter will be... If the dual-terminal DC / AC voltage source converter operates in islanded independent power supply mode, then the output power of the dual-terminal DC / AC voltage source converter is equal to the load power. If the dual-terminal DC / AC voltage source converter operates in islanded cooperative power supply mode, then the sum of the power output of the diesel generator and the power output of the dual-terminal DC / AC voltage source converter equals the load power. And the power output of the diesel generator for The power output of a dual-terminal DC / AC voltage source converter for ;in, This refers to the rated apparent power of a two-terminal DC / AC voltage source converter. This refers to the rated apparent power of the diesel generator; if the dual-terminal DC / AC voltage source converter operates in islanded long-term operation mode, then the output power of the dual-terminal DC / AC voltage source converter is the minimum set power. And the power output of the diesel generator satisfy ;

[0022] The following formula is used to control the dual-terminal DC / AC voltage source converter:

[0023] In the formula The mechanical power provided to the prime mover; This is the droop coefficient; The rated angular frequency of the output of a dual-terminal DC / AC voltage source converter; This is the actual angular frequency output of the dual-terminal DC / AC voltage source converter. The phase angle of the excitation electromotive force; It is the moment of inertia; The electromagnetic power output of a dual-terminal DC / AC voltage source converter; The damping coefficient;

[0024] The output voltage amplitude of a dual-terminal DC / AC voltage source converter is calculated using the following formula. To take control:

[0025] In the formula, The integral coefficient; This is a reference value for the reactive power output of a dual-terminal DC / AC voltage source converter. This is the droop control coefficient; This is the reference voltage output by the dual-terminal DC / AC voltage source converter; This refers to the actual output voltage of the dual-terminal DC / AC voltage source converter.

[0026] The reference value of the d-axis current of the dual-terminal DC / AC voltage source converter is calculated using the following formula. and q-axis current reference value :

[0027] In the formula This is the d-axis reference voltage; This is the proportionality coefficient; The integral coefficient; This is the q-axis reference voltage;

[0028] The d-axis voltage modulation value of the dual-terminal DC / AC voltage source converter is calculated using the following formula. and q-axis voltage modulation value :

[0029] In the formula This is the proportionality coefficient of the inner current loop; The integral coefficient of the inner current loop; This is the inductance value of the filter inductor;

[0030] Modulate the d-axis voltage value and q-axis voltage modulation value pass After conversion, a control signal is generated using PWM modulation to control the dual-terminal DC / AC voltage source converter.

[0031] The present invention provides an emergency power supply system for urban power distribution networks and a control method thereof, which connects a diesel generator and an energy storage converter in parallel. Through the innovative design of the emergency power supply system for urban power distribution networks, and in combination with the voltage signal of the corresponding common connection point, four corresponding operating schemes are designed and corresponding control methods are given. This not only realizes emergency power supply for the power distribution network, but also has higher reliability and better accuracy. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the system of the present invention. Detailed Implementation

[0033] like Figure 1 The diagram shown is a structural schematic of the system of the present invention: The urban power distribution network emergency power supply system disclosed in this invention, which connects a diesel generator and an energy storage converter in parallel, includes a diesel generator (DG) and an energy storage device (ESS), as well as a diesel generator grid connection switch (K2), a dual-terminal DC / DC voltage source converter (VSC2), and a DC-side capacitor. The system consists of a dual-terminal DC / AC voltage source converter VSC1 and a filter module; the distribution network G1 is connected to the point of common coupling (PCC) via the distribution network grid-connection switch K1; the load L1 is directly connected to the PCC; the diesel generator is connected to the PCC via a series-connected diesel generator grid-connection switch; the energy storage device is connected to one end of the dual-terminal DC / DC voltage source converter, the other end of the dual-terminal DC / DC voltage source converter is connected to the DC terminal of the dual-terminal DC / AC voltage source converter, and the AC terminal of the dual-terminal DC / AC voltage source converter is connected to the PCC via the filter module; and the DC-side capacitor is connected in parallel between the positive and negative input terminals of the DC terminal of the dual-terminal DC / AC voltage source converter.

[0034] In specific implementation, the dual-terminal DC / DC voltage source converter adopts a constant DC bus voltage control scheme to provide stable DC voltage support for the DC end of the dual-terminal DC / AC voltage source converter; the dual-terminal DC / AC voltage source converter can operate in grid-connected or islanded mode, and adopts a virtual synchronous generator control scheme.

[0035] As a preferred embodiment, the filtering module is an RLC filtering module; this filtering module is used to filter out harmonic components in the AC output of VSC1, optimize power quality, ensure that the voltage and current waveforms connected to the PCC point meet the power supply standards, and provide a waveform basis for the stable operation of the VSG control strategy.

[0036] Meanwhile, the present invention also discloses a control method for an urban power distribution network emergency power supply system in which the diesel generator and energy storage converter are connected in parallel, comprising the following steps:

[0037] The control method described is a control method for a dual-terminal DC / AC voltage source converter;

[0038] The operating modes of dual-terminal DC / AC voltage source converters include grid-connected operation mode, islanded independent power supply mode, islanded collaborative power supply mode, and islanded long-term operation mode;

[0039] Grid-connected operation mode: When the voltage at the point of common coupling is higher than the set value, the grid-connected switch of the distribution network is closed, and the grid-connected switch of the diesel generator is opened; the dual-terminal DC / AC voltage source converter is in constant power control mode and outputs rated power; at this time, the emergency power supply system of the distribution network and the distribution network operate in parallel and jointly supply power to the load;

[0040] Isolated power supply mode: When the grid connection switch of the distribution network is open, the voltage of the point of common coupling is lower than the set value (preferably 0.9 per unit), and the rated power of the dual-terminal DC / AC voltage source converter is greater than the load power, the grid connection switch of the diesel generator is open, the dual-terminal DC / AC voltage source converter is in load tracking mode, and outputs according to the load power; at this time, the energy storage device supplies power to the load independently; at this time, the diesel generator is in a hot standby state to maintain its rated capacity;

[0041] Islanded Cooperative Power Supply Mode: When the distribution network grid connection switch is open, the voltage at the point of common coupling is lower than the set value (preferably 0.9 per unit), and the rated power of the dual-terminal DC / AC voltage source converter is less than the load power, the diesel generator grid connection switch is closed, and the diesel generator is connected to the point of common coupling. The diesel generator and the dual-terminal DC / AC voltage source converter distribute their output power according to their own capacity to ensure that the sum of the output power of the diesel generator and the output power of the energy storage device meets the load requirements. At this time, the diesel generator and the energy storage device work together to supply power to the load.

[0042] Islanded Long-Term Operation Mode: When the dual-terminal DC / AC voltage source converter is in islanded independent power supply mode or islanded collaborative power supply mode, and the remaining capacity of the energy storage device reaches the set lower limit, the grid connection switch of the diesel generator is closed, and the diesel generator supplies power to the load; the dual-terminal DC / AC voltage source converter only outputs the minimum set power and maintains a constant output; at this time, the diesel generator DG acts as the main power supply unit, undertaking the main load power supply and ensuring that the core power supply needs are met;

[0043] The above four working modes are well applicable to various operating conditions of the power distribution network.

[0044] In practice, the control process of a dual-terminal DC / AC voltage source converter includes the following steps:

[0045] Acquire the output voltage, output current, and common coupling point voltage data of the dual-terminal DC / AC voltage source converter;

[0046] Based on the obtained output voltage of the dual-terminal DC / AC voltage source converter and output current ,go through Decomposition yields the d-axis voltage. q-axis voltage d-axis current and q-axis current The output active power of the dual-terminal DC / AC voltage source converter was calculated. for The output reactive power of the dual-terminal DC / AC voltage source converter was calculated. for ;

[0047] If the dual-terminal DC / AC voltage source converter operates in grid-connected mode, the rated power output of the dual-terminal DC / AC voltage source converter will be... If the dual-terminal DC / AC voltage source converter operates in islanded independent power supply mode, then the output power of the dual-terminal DC / AC voltage source converter is equal to the load power. If the dual-terminal DC / AC voltage source converter operates in islanded cooperative power supply mode, then the sum of the power output of the diesel generator and the power output of the dual-terminal DC / AC voltage source converter equals the load power. And the power output of the diesel generator for The power output of a dual-terminal DC / AC voltage source converter for ;in, This refers to the rated apparent power of a two-terminal DC / AC voltage source converter. This refers to the rated apparent power of the diesel generator; if the dual-terminal DC / AC voltage source converter operates in islanded long-term operation mode, then the output power of the dual-terminal DC / AC voltage source converter is the minimum set power. And the power output of the diesel generator satisfy ;

[0048] The following formula is used to control the dual-terminal DC / AC voltage source converter:

[0049] In the formula The mechanical power provided to the prime mover; This is the droop coefficient; The rated angular frequency of the output of a dual-terminal DC / AC voltage source converter; This is the actual angular frequency output of the dual-terminal DC / AC voltage source converter. The phase angle of the excitation electromotive force; It is the moment of inertia; The electromagnetic power output of a dual-terminal DC / AC voltage source converter; The damping coefficient is used to achieve frequency deviation suppression and on-demand distribution of active power. It maintains system frequency stability during islanded operation and distributes active power to diesel generators according to capacity during collaborative power supply.

[0050] The output voltage amplitude of a dual-terminal DC / AC voltage source converter is calculated using the following formula. To take control:

[0051] In the formula, The integral coefficient; This is a reference value for the reactive power output of a dual-terminal DC / AC voltage source converter. This is the droop control coefficient; This is the reference voltage output by the dual-terminal DC / AC voltage source converter; This is the actual output voltage of the dual-terminal DC / AC voltage source converter; this control scheme is used to simulate the voltage-reactive excitation regulation characteristics of a synchronous generator, and adjusts the output voltage amplitude of the VSG according to the reactive power difference and voltage deviation to achieve output voltage stability and reactive power regulation.

[0052] The reference value of the d-axis current of the dual-terminal DC / AC voltage source converter is calculated using the following formula. and q-axis current reference value :

[0053] In the formula This is the d-axis reference voltage; This is the proportionality coefficient; The integral coefficient; This is the q-axis reference voltage;

[0054] The d-axis voltage modulation value of the dual-terminal DC / AC voltage source converter is calculated using the following formula. and q-axis voltage modulation value :

[0055] In the formula This is the proportionality coefficient of the inner current loop; The integral coefficient of the inner current loop; This is the inductance value of the filter inductor;

[0056] Modulate the d-axis voltage value and q-axis voltage modulation value pass After conversion, a control signal is generated using PWM modulation to control the dual-terminal DC / AC voltage source converter.

[0057] The control scheme of this invention responds quickly to changes in DC power during the transient process of switching from grid connection to islanding, suppresses DC voltage drops or spikes, and ensures that the VSC1 control loop does not become unstable due to input voltage fluctuations; when VSC1 is running in parallel with the diesel generator, it provides voltage feedforward support for VSC1 and improves the dynamic characteristics of power distribution; when the energy storage device has low power, it prevents over-discharge of the battery by limiting the range of DC voltage fluctuations, thus extending the life of the energy storage system.

Claims

1. An emergency power supply system for urban power distribution networks, comprising a diesel generator and an energy storage converter connected in parallel, characterized in that... It also includes a diesel generator grid-connection switch, a dual-terminal DC / DC voltage source converter, a DC-side capacitor, a dual-terminal DC / AC voltage source converter, and a filter module; the distribution network is connected to the point of common coupling (PCC) through the grid-connection switch; the load is directly connected to the PCC; the diesel generator is connected to the PCC through a series-connected diesel generator grid-connection switch; the energy storage device is connected to one end of the dual-terminal DC / DC voltage source converter, the other end of the dual-terminal DC / DC voltage source converter is connected to the DC terminal of the dual-terminal DC / AC voltage source converter, and the AC terminal of the dual-terminal DC / AC voltage source converter is connected to the PCC through the filter module; the DC-side capacitor is connected in parallel between the positive and negative input terminals of the DC terminal of the dual-terminal DC / AC voltage source converter.

2. The urban power distribution network emergency power supply system with diesel generator and energy storage converter connected in parallel according to claim 1, characterized in that... The dual-terminal DC / DC voltage source converter adopts a constant DC bus voltage control scheme to provide stable DC voltage support for the DC terminal of the dual-terminal DC / AC voltage source converter; the dual-terminal DC / AC voltage source converter can operate in grid-connected or islanded mode, and adopts a virtual synchronous generator control scheme.

3. The urban power distribution network emergency power supply system with diesel generator and energy storage converter connected in parallel according to claim 1, characterized in that... The filtering module is an RLC filtering module.

4. A control method for an urban power distribution network emergency power supply system with a diesel generator and an energy storage converter connected in parallel, as described in any one of claims 1 to 3, characterized in that... Includes the following steps: The control method described is a control method for a dual-terminal DC / AC voltage source converter; The operating modes of dual-terminal DC / AC voltage source converters include grid-connected operation mode, islanded independent power supply mode, islanded collaborative power supply mode, and islanded long-term operation mode; Grid-connected operation mode: When the voltage at the point of common coupling is higher than the set value, the grid-connected switch of the distribution network is closed, and the grid-connected switch of the diesel generator is opened; the dual-terminal DC / AC voltage source converter is in constant power control mode and outputs rated power; at this time, the emergency power supply system of the distribution network and the distribution network operate in parallel and jointly supply power to the load; Isolated power supply mode: When the grid connection switch of the distribution network is open, the voltage of the common connection point is lower than the set value, and the rated power of the dual-terminal DC / AC voltage source converter is greater than the load power, the grid connection switch of the diesel generator is open, the dual-terminal DC / AC voltage source converter is in load tracking mode, and outputs according to the load power; at this time, the energy storage device supplies power to the load independently. Islanded Cooperative Power Supply Mode: When the grid connection switch of the distribution network is open, the voltage at the point of common coupling is lower than the set value, and the rated power of the dual-terminal DC / AC voltage source converter is less than the load power, the grid connection switch of the diesel generator is closed, and the diesel generator is connected to the point of common coupling. The diesel generator and the dual-terminal DC / AC voltage source converter distribute the output power according to their own capacity to ensure that the sum of the output power of the diesel generator and the output power of the energy storage device meets the load requirements. At this time, the diesel generator and the energy storage device work together to supply power to the load. Islanded long-term operation mode: When the dual-terminal DC / AC voltage source converter is in islanded independent power supply mode or islanded collaborative power supply mode, and the remaining capacity of the energy storage device reaches the set lower limit, the grid connection switch of the diesel generator is closed, and the diesel generator supplies power to the load; the dual-terminal DC / AC voltage source converter only outputs the minimum set power and keeps the output constant.

5. The control method according to claim 4, characterized in that... The voltage setting at the point of common coupling is 0.9 per unit.

6. The control method according to claim 5, characterized in that... The control process of a two-terminal DC / AC voltage source converter includes the following steps: Acquire the output voltage, output current, and common coupling point voltage data of the dual-terminal DC / AC voltage source converter; Based on the obtained output voltage of the dual-terminal DC / AC voltage source converter and output current ,go through Decomposition yields the d-axis voltage. q-axis voltage d-axis current and q-axis current ; The output active power of the dual-terminal DC / AC voltage source converter was calculated. for The output reactive power of the dual-terminal DC / AC voltage source converter was calculated. for ; If the dual-terminal DC / AC voltage source converter operates in grid-connected mode, the rated power output of the dual-terminal DC / AC voltage source converter will be... If the dual-terminal DC / AC voltage source converter operates in islanded independent power supply mode, then the output power of the dual-terminal DC / AC voltage source converter is equal to the load power. If the dual-terminal DC / AC voltage source converter operates in islanded cooperative power supply mode, then the sum of the power output of the diesel generator and the power output of the dual-terminal DC / AC voltage source converter equals the load power. And the power output of the diesel generator for The power output of a dual-terminal DC / AC voltage source converter for ;in, This refers to the rated apparent power of a two-terminal DC / AC voltage source converter. This refers to the rated apparent power of the diesel generator; if the dual-terminal DC / AC voltage source converter operates in islanded long-term operation mode, then the output power of the dual-terminal DC / AC voltage source converter is the minimum set power. And the power output of the diesel generator satisfy ; The following formula is used to control the dual-terminal DC / AC voltage source converter: In the formula The mechanical power provided to the prime mover; This is the droop coefficient; The rated angular frequency of the output of a dual-terminal DC / AC voltage source converter; This is the actual angular frequency output of the dual-terminal DC / AC voltage source converter. The phase angle of the excitation electromotive force; It is the moment of inertia; The electromagnetic power output of a dual-terminal DC / AC voltage source converter; The damping coefficient; The output voltage amplitude of a dual-terminal DC / AC voltage source converter is calculated using the following formula. To take control: In the formula, The integral coefficient; This is a reference value for the reactive power output of a dual-terminal DC / AC voltage source converter. This is the droop control coefficient; This is the reference voltage output by the dual-terminal DC / AC voltage source converter; This refers to the actual output voltage of the dual-terminal DC / AC voltage source converter. The reference value of the d-axis current of the dual-terminal DC / AC voltage source converter is calculated using the following formula. and q-axis current reference value : In the formula This is the d-axis reference voltage; This is the proportionality coefficient; The integral coefficient; This is the q-axis reference voltage; The d-axis voltage modulation value of the dual-terminal DC / AC voltage source converter is calculated using the following formula. and q-axis voltage modulation value : In the formula This is the proportionality coefficient of the inner current loop; The integral coefficient of the inner current loop; This is the inductance value of the filter inductor; Modulate the d-axis voltage value and q-axis voltage modulation value pass After conversion, a control signal is generated using PWM modulation to control the dual-terminal DC / AC voltage source converter.

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