A control method for parallel operation of energy storage converter and generator set to withstand impact loads

Abstract

This application relates to a control method for parallel operation of an energy storage converter and a generator set to withstand impact loads. The method includes: establishing a control framework for the energy storage converter based on the circuit topology of the energy storage converter and a rotating coordinate system DQ-axis voltage-current control method; connecting a voltage and frequency error droop loop in parallel to the current setpoint of the phase-locked loop current-source inverter within the energy storage converter control framework; and controlling the operation of the energy storage converter after the current loop using an SVPWM modulation strategy. This application achieves stable operation of the energy storage converter and the system, ensuring that when the system starts up with wind turbine-type impact loads, the converter participates in the stable control of the AC bus, dynamically and evenly distributes the impact current, enabling smooth load startup and operation; and dynamically adjusts the power of the energy storage converter in steady state, allowing the diesel generator set to operate at economical power.

Description

Technical Field

[0001] This application relates to the fields of microgrids and energy storage operation control, and in particular to a control method for parallel connection of energy storage converter and generator set to resist impact load. Background Technology

[0002] The energy storage converter operates under a droop-controlled voltage source inverter, achieving good transient power sharing. However, the control structure is complex and lacks robustness. The power sharing effect is sensitive to the selection of model parameters. For different diesel generator units, their inertia and damping are different, and the energy storage converter must adapt to different inertia and damping parameters. The engineering parameter tuning and debugging are difficult. At the same time, for microgrid systems composed of multiple diesel generator units and energy storage converters, the engineering reliability and applicability need further research.

[0003] Energy storage converters operate as phase-locked loop current-source inverters. When load changes suddenly occur, energy storage converters have difficulty responding quickly to active and reactive power. They also lack reactive power sharing control strategies. Moreover, when motor loads start, the main impact is reactive current surge. When diesel generators and energy storage converters are connected in parallel to start high-power motor loads, they are prone to starting failure due to load voltage loss. In addition, unbalanced load power is mainly responded to by diesel generators, causing system frequency and voltage fluctuations, which bring instability risks. Summary of the Invention

[0004] In order to reduce the instability risk caused by the system frequency and voltage fluctuations due to the unbalanced load power mainly being responded to by the diesel generator set, this application provides a control method for the parallel connection of an energy storage converter and a generator set to resist impact loads.

[0005] The control method for parallel connection of an energy storage converter and a generator set to resist impact loads provided in this application adopts the following technical solution:

[0006] A control method for a parallel-connected energy storage converter and generator set to withstand impact loads includes:

[0007] Based on the circuit topology of the energy storage converter, a control framework for the energy storage converter is established based on the DQ-axis voltage and current control method of the rotating coordinate system.

[0008] In the energy storage converter control framework, a drooping loop for voltage and frequency error is connected in parallel to the current setpoint of the phase-locked loop current-source inverter; after the current loop, the energy storage converter is controlled by an SVPWM modulation strategy.

[0009] By adopting the above technical solution, a control strategy for parallel connection of energy storage converter and diesel generator unit to handle impact loads is realized. This ensures the stable operation of the parallel system and guarantees that when the parallel system starts up wind turbine-type impact loads, the energy storage converter participates in the AC bus stability control. The energy storage converter dynamically shares the impact current, enabling the load to start up smoothly. In steady state, the power of the energy storage converter is dynamically adjusted so that the diesel generator unit operates at economic power. This satisfies the starting and stable operation of the impact load under conditions where the capacity of the energy storage converter and the diesel generator unit are comparable. It also reduces the instability risk caused by the diesel generator unit mainly responding to unbalanced load power, which leads to system frequency and voltage fluctuations.

[0010] Optionally, the step of establishing a control framework for the energy storage converter based on the current topology of the energy storage converter and the voltage and current control method of the rotating coordinate system DQ axis includes:

[0011] Based on the current topology of the energy storage converter, the output current, output voltage, and load current of the energy storage converter are acquired; the DQ component, angular frequency, and phase angle of the microgrid voltage are obtained through the generalized second-order integral DSOGI software phase-locked loop and PARK transform.

[0012] The output current and load current DQ components are obtained based on the phase angle via a synchronous coordinate system.

[0013] Optionally, the step of establishing an energy storage converter control framework based on the current topology of the energy storage converter and the rotating coordinate system DQ axis voltage and current control method further includes:

[0014] Obtain the active and reactive power output of the diesel generator;

[0015] The current command of the energy storage converter current loop is obtained based on the load current DQ component, the given active power output of the diesel generator, and the reactive power.

[0016] Optionally, the active and reactive power output of the diesel generator is 0.75 times the economic power, i.e., the rated power, of the diesel generator unit.

[0017] Optionally, the current-source voltage and frequency error droop loop connected in parallel to the phase-locked loop current-source inverter in the energy storage converter control framework includes:

[0018] Based on the current topology of the energy storage converter, the output current, output voltage and load current of the energy storage converter are collected.

[0019] The DQ components, angular frequency, and phase angle of the microgrid voltage are obtained through a generalized second-order integral DSOGI software phase-locked loop and PARK transform.

[0020] Based on the phase angle, the output current and load current DQ components are obtained through a synchronous coordinate system;

[0021] Based on the obtained microgrid voltage angular frequency, the difference between the angular frequency and the system rated angular frequency is used to obtain the D-axis current command of the energy storage converter current loop through the frequency active control loop.

[0022] The voltage amplitude is obtained from the DQ component of the microgrid voltage. The Q-axis current command of the energy storage converter current loop is obtained through the voltage reactive current control loop based on the difference between the system rated voltage and the microgrid voltage amplitude.

[0023] Optionally, the current-source voltage and frequency error droop loop of the phase-locked loop current-source inverter in the energy storage converter control framework further includes:

[0024] Obtain the active and reactive power output of the diesel generator;

[0025] The current command of the energy storage converter current loop is obtained based on the load current DQ component, the given active power output of the diesel generator, and the reactive power.

[0026] The DQ-axis reference current command of the energy storage converter current loop is obtained by adding the obtained current command of the energy storage converter and the DQ-axis current command after passing through a first-order inertial filter.

[0027] Optionally, controlling the energy storage converter via an SVPWM modulation strategy after the current loop includes:

[0028] Based on the current topology of the energy storage converter, the output current, output voltage and load current of the energy storage converter are collected.

[0029] The DQ components, angular frequency, and phase angle of the microgrid voltage are obtained through a generalized second-order integral DSOGI software phase-locked loop and PARK transform.

[0030] Based on the phase angle, the output current and load current DQ components are obtained through a synchronous coordinate system;

[0031] Based on the obtained microgrid voltage angular frequency, the difference between the angular frequency and the system rated angular frequency is used to obtain the D-axis current command of the energy storage converter current loop through the frequency active control loop.

[0032] The voltage amplitude is obtained from the DQ component of the obtained microgrid voltage. The Q-axis current command of the energy storage converter current loop is obtained through the voltage reactive current control loop based on the difference between the system rated voltage and the microgrid voltage amplitude.

[0033] Obtain the active and reactive power output of the diesel generator;

[0034] The current command of the energy storage converter current loop is obtained based on the load current DQ component, the given active power output of the diesel generator, and the reactive power.

[0035] The DQ-axis reference current command of the energy storage converter current loop is obtained by adding the obtained current command of the energy storage converter and the DQ-axis current command after passing through a first-order inertial filter.

[0036] The control signal is obtained by using the current control equation based on the acquired DQ axis reference current command and output current.

[0037] Optionally, the step of controlling the operation of the energy storage converter after the current loop via SVPWM modulation strategy further includes: obtaining the PWM control signal of the energy storage converter switching transistor by inverse coordinate transformation and SVPWM modulation based on the phase angle between the control signal and the microgrid voltage.

[0038] The operation of the energy storage converter is controlled based on the PWM control signal.

[0039] In summary, this application includes at least one of the following beneficial technical effects:

[0040] 1. Effectively enables the simultaneous start-up of the diesel generator and the energy storage converter under impact load when the capacity of the energy storage converter and the diesel generator is comparable to the load capacity, thus avoiding the situation of "oversized generator for small load" and eliminating the need to configure an overcapacity diesel generator.

[0041] 2. When the diesel and storage system is started in parallel under impact load, the PI control and droop circuit are organically combined to autonomously distribute the inrush current during the start-up process. This avoids the situation where one of the parallel systems stops due to overcurrent during the start-up of an impact load, which would cause the entire parallel system to stop or the AC voltage to be too low, ultimately leading to load start-up failure.

[0042] 3. After the load starts, the system can effectively control the output power of the diesel generator, so that the diesel generator unit works at its maximum efficiency. Under stable load operation, if the battery has sufficient power, the diesel generator can be shut down and the energy storage converter can seamlessly switch from grid-connected operation to VF off-grid operation to run independently under load. When the battery is almost depleted, the diesel generator is restarted and the energy storage converter switches to grid-connected operation, controlling the diesel generator to work at its maximum efficiency, and the excess load energy is used to charge the battery. Attached Figure Description

[0043] Figure 1 This is a topology diagram of the energy storage converter in a control method for parallel connection of an energy storage converter and a generator set to resist impact loads according to an embodiment of this application;

[0044] Figure 2 This is a structural diagram of the diesel-storage system in a control method for parallel connection of an energy storage converter and a generator set to resist impact loads according to an embodiment of this application;

[0045] Figure 3This is a control block diagram of a control method for a parallel-connected energy storage converter and generator set to withstand impact loads according to an embodiment of this application.

[0046] Figure 4 This is a waveform diagram of the startup process of the energy storage converter and the air compressor of the diesel generator in a control method for parallel connection of an energy storage converter and a generator set to resist impact load according to an embodiment of this application;

[0047] Figure 5 This is a waveform diagram of the energy storage converter and the air compressor of the diesel generator parallel unit in a control method for a parallel connection of an energy storage converter and a generator set to resist impact loads according to an embodiment of this application.

[0048] Figure 6 This is a waveform diagram of the instantaneous transition from star-connected to delta-connected start-up operation in a control method for parallel connection of an energy storage converter and a generator set to resist impact loads, according to an embodiment of this application. Detailed Implementation

[0049] The present application will be further described in detail below with reference to the accompanying drawings.

[0050] In many remote areas, such as islands and construction sites, it is difficult to connect to a stable main power grid or the power equipment capacity is insufficient due to long power transmission distances, difficult power construction, or temporary power demand. In these situations, diesel generator sets are often the primary power source. With the development of microgrids and energy storage technologies, diesel-powered microgrid systems (hereinafter referred to as "the system"), including diesel generator sets (hereinafter referred to as "diesel generator sets" or "diesel generators") and energy storage converters, have become an important development direction in microgrid systems due to their ability to increase capacity through parallel connection and effectively improve the efficiency of diesel generator sets.

[0051] Energy storage converters are generally controlled as droop voltage-source inverters or phase-locked loop current-source inverters. Droop-controlled voltage source inverters, by introducing inertia and damping into the inverter—a technique known as virtual synchronous generator technology—give the inverter and diesel generator units similar mechanical characteristics. This allows the energy storage converter and the diesel generator unit to share the inrush current during startup, improving microgrid stability. However, this method has a complex control structure, weak robustness, and the sharing effect is sensitive to the selection of model parameters. Different diesel generator units have different inertia and damping parameters, requiring the energy storage converter to adapt to different inertia and damping parameters, making engineering parameter tuning and debugging difficult.

[0052] When the energy storage converter is controlled as a phase-locked loop current-source inverter, the diesel generator unit is responsible for maintaining constant system voltage and frequency during operation. Based on load current transients and changes in AC voltage and frequency, the upper-level energy management system dynamically adjusts the active current command to ensure its output power tracks load disturbances. However, during sudden load changes, the energy storage converter struggles to respond quickly to both active and reactive power. Furthermore, the lack of reactive power sharing and unbalanced power control strategies means that reactive current surges and unbalanced load power are primarily handled by the diesel generator unit, causing system frequency and voltage fluctuations and introducing instability risks.

[0053] Existing parallel control methods for diesel and energy storage mainly target the parallel connection of energy storage converters and large-capacity diesel generators. When the capacity of the energy storage converter and the diesel generator unit is similar, there are very few control methods that can start operation only when the load is suddenly added or unloaded due to impact loads, and the impact power of the load is greater than the capacity of the diesel generator unit and also greater than the capacity of the energy storage converter. In other words, there are very few control methods that can start operation only when the generator and the generator unit work together in parallel.

[0054] In summary, the existing energy storage converter control technology is insufficient to meet the requirements of starting up and stable operation under impact loads when the capacity of the energy storage converter and the diesel generator are comparable.

[0055] To address the aforementioned issues, this application discloses a control method for parallel-connected energy storage converters and generator sets to withstand impact loads. This method aims to achieve stable operation of the parallel-connected system of energy storage converters and diesel generator sets, ensuring that when the parallel system starts up wind turbine-type impact loads, the energy storage converter participates in the stable control of the AC bus. This allows the energy storage converter to dynamically share the impact current, enabling the load to start up and run smoothly. In steady state, the power of the energy storage converter is dynamically adjusted so that the diesel generator set operates at economical power.

[0056] A control method for a parallel-connected energy storage converter and generator set to withstand impact loads includes:

[0057] S110. Based on the circuit topology of the energy storage converter, establish the control framework of the energy storage converter based on the DQ axis voltage and current control method of the rotating coordinate system.

[0058] Among them, the energy storage converter topology is as follows Figure 1 As shown, the system structure is as follows Figure 2 As shown, the AC terminal of the energy storage converter is equipped with a load interface and a mains interface. The diesel generator unit is connected to the mains interface of the energy storage converter, and the load is connected to the load interface of the energy storage converter.

[0059] S120, A drooping loop for voltage and frequency error is connected in parallel to the current setpoint of the phase-locked loop current-source inverter in the energy storage converter control framework.

[0060] S130, after the current loop, controls the operation of the energy storage converter through SVPWM modulation strategy.

[0061] In order to increase the capacity and improve the working efficiency of diesel generator units, energy storage converters are being equipped for diesel generator units to form diesel-storage microgrid power supply systems, which are becoming increasingly widespread. For wind turbines, air compressors, water pumps and electric impulsive loads, the starting current is 5-10 times the rated current. In order to ensure that the parallel system can withstand the impact and start up smoothly, the energy storage converter is generally controlled as a droop voltage-type inverter or a phase-locked loop current-type inverter.

[0062] The droop-controlled voltage source inverter introduces inertia and damping, i.e., virtual synchronous generator technology, to make the inverter have similar mechanical characteristics to the diesel generator unit. This allows the energy storage converter and the diesel generator unit to share the inrush current during startup, thus improving the stability of the microgrid.

[0063] When the energy storage converter is controlled as a phase-locked loop current-type inverter, the diesel generator unit is responsible for maintaining constant system voltage and frequency during operation. Based on the transient load current and changes in AC voltage and frequency, the upper-level energy management system dynamically adjusts the active current command so that its output power can track the changes in load disturbance.

[0064] The system has a DC bus voltage Udc of 700V, an effective AC output voltage of 400 / 50Hz, a rated capacity of 500kW, an L1 filter of 0.1mH, a C filter of 200uF, an L2 filter of 0.0125mH, a switching frequency of 2.8k, and an isolation transformer of 500kVA 315 / 400V Dyn11 type.

[0065] Referring to the figure, based on the circuit topology of the energy storage converter, a control framework for the energy storage converter is established using the DQ-axis voltage and current control method in a rotating coordinate system, including:

[0066] S210. Based on the current topology of the energy storage converter, acquire the output current, output voltage and load current of the energy storage converter.

[0067] Referring to the current topology diagram of the energy storage converter, the output currents of the energy storage converter are collected as i ao i bo i co The output voltages are u a u b u c The load currents are i a_Load i b_Load i c_Load .

[0068] S220, through generalized second-order integral DSOGI software phase-locked loop and PARK transform, obtains the DQ component, angular frequency and phase angle of the microgrid voltage.

[0069] Wherein, the DQ components of the microgrid voltage are respectively set as u d u q The angular frequency is w, and the phase angle is θ.

[0070] S230. Based on the phase angle, obtain the output current and load current DQ components through the synchronous coordinate system.

[0071] Among them, the DQ components of the load current are i do i qo i d_load i q_load In this embodiment, the line voltage and current sampling are calibrated to 4096, representing the rated value, and the digital angular frequency is calibrated to 9600 according to Q10, representing 314.159 rad / s.

[0072] S240. Based on the obtained microgrid voltage angular frequency, the difference between the obtained angular frequency and the system rated angular frequency is used to obtain the D-axis current command of the energy storage converter current loop through the frequency active control loop.

[0073] The rated active power output of the diesel generator in the system is set as P. G The reactive power is set to Q. G The current command of the energy storage converter current loop is set to I. dref1 I qref1 The calculation equation is:

[0074] I dref1 =i d_load -I d_G

[0075] I qref1 =i q_load -I q_G

[0076] In the formula, I d_G and I q_G The active power PG and reactive power QG of the diesel generator were calculated using the following equations:

[0077]

[0078] In this embodiment, the active power and reactive power are normalized, and the calibration is 4096 to represent the rated value.

[0079] S250: The voltage amplitude is obtained based on the DQ component of the obtained microgrid voltage. The Q-axis current command of the energy storage converter current loop is obtained through the voltage reactive current control loop based on the difference between the system rated voltage and the microgrid voltage amplitude.

[0080] The difference between the microgrid voltage angular frequency obtained from the above steps and the system rated angular frequency is used to obtain the D-axis current command I of the energy storage converter current loop through the frequency active power control loop. dref2 The voltage amplitude u is obtained from the DQ component of the microgrid voltage obtained in step 1. m The difference between the system rated voltage and the microgrid voltage amplitude is used by the voltage reactive current control loop to obtain the Q-axis current command I of the energy storage converter current loop. qref2 .

[0081] I dref2 and I qref2 The calculation equation is as follows:

[0082]

[0083] In the formula, K p_f K q_u K is the proportionality coefficient, equivalent to the reciprocal of the droop coefficients Pf and QU. i_w K i_u is the integral coefficient.

[0084] Furthermore, in this implementation example, the Pf droop coefficient is set to 100% of the active power change, and the frequency change is within 2%. In this example, the QU droop factor is set to 100% for reactive power change, and the voltage amplitude change is within 10%.

[0085] Integral parameter K i_w K i_u Set it to 0.85.

[0086] Referring to the figure, the current-source voltage and frequency error droop loop in the phase-locked loop current-source inverter of the energy storage converter control framework includes:

[0087] S310. Obtain the active and reactive power output of the diesel generator;

[0088] S320. Obtain the current command of the energy storage converter current loop based on the load current DQ component, the given active power output of the diesel generator, and the reactive power.

[0089] S330. The DQ-axis reference current command of the energy storage converter current loop is obtained by adding the obtained current command of the energy storage converter and the DQ-axis current command after first-order inertial filtering.

[0090] Among them, the DQ axis current command I obtained according to the above steps dref1 I qref1 and DQ axis current command I dref2 I qref2The summation yields the DQ-axis reference current command I of the energy storage converter current loop. dref I qref , among which, I dref I qref The calculation formula is:

[0091]

[0092] In the formula, T is the time constant of the first-order inertial filter, and s is the Laplace operator. In this example, T is set to 20ms.

[0093] Referring to the figure, the energy storage converter is controlled by an SVPWM modulation strategy after the current loop, including:

[0094] S410. Based on the phase angle between the control signal and the microgrid voltage, the PWM control signal of the energy storage converter switching transistor is obtained through inverse coordinate transformation and SVPWM modulation.

[0095] Among them, the DQ axis reference current command I obtained according to the above steps dref I qref and the obtained output current i do i qo The control signal U is obtained through the current control equation. d U q The current control equation is:

[0096]

[0097] In the formula, Kp is the proportional coefficient of the current loop and Ki is the integral coefficient of the current loop. In this example, Kp is set to 0.19 and Ki is set to 2.56.

[0098] S420. Control the operation of the energy storage converter based on the PWM control signal.

[0099] Among them, the control signal U obtained according to the above steps d U q The obtained microgrid voltage phase angle is used to obtain the PWM control signal of the energy storage converter switching transistor through inverse coordinate transformation and SVPWN modulation.

[0100] The waveforms during the startup and operation of the diesel storage parallel air compressor in this example are as follows: Figure 4 , Figure 5 and Figure 6 As shown, Figure 4 This represents the waveform during the startup process of the energy storage converter and the diesel generator parallel air compressor. Figure 5 This represents the waveform at the moment of startup of the energy storage converter and the diesel generator parallel air compressor. Figure 6 The instantaneous waveform of an air compressor during star-connected start-up and delta-connected operation. Figure 4 and Figure 5The waveform in the image is sword-shaped. Figure 4 In the diagram, the portion between the blade and scabbard, as well as the guard, represents the load current; the portion between the blade and hilt represents the generator output current; and the portion of the scabbard and the outer end of the hilt represents the line voltage. Figure 5 In the diagram, the guard represents the load current, the blade and hilt represent the generator output current, and the scabbard and the outer end of the hilt represent the line voltage. Figure 6 In the diagram, the line with the largest amplitude represents the load current, followed by the diesel generator output current, and the line with the smallest amplitude represents the line voltage. Figure 4 , Figure 5 and Figure 6 It can be seen that the inrush current at the moment of air compressor startup and during the transition from star to delta configuration is much greater than the operating current. In this example, the energy storage converter and the diesel generator share the inrush current during startup, which ensures the voltage quality during the startup process.

[0101] The implementation principle of the control method for parallel anti-impact load of energy storage converter and generator set in this application embodiment is as follows: According to the circuit topology of energy storage converter, the converter control framework is established based on the rotating coordinate system DQ axis voltage and current control method. A voltage and frequency error droop loop is connected in parallel on the current setpoint of the traditional phase-locked loop current-type inverter, and then the converter operation is controlled by the SVPWM modulation strategy.

[0102] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A control method for a parallel-connected energy storage converter and generator set to withstand impact loads, characterized in that, include: Based on the circuit topology of the energy storage converter, a control framework for the energy storage converter is established based on the DQ-axis voltage and current control method of the rotating coordinate system. In the energy storage converter control framework, a drooping loop for voltage and frequency error is connected in parallel to the current setpoint of the phase-locked loop current-source inverter. The energy storage converter is controlled by an SVPWM modulation strategy after the current loop. The current-source current-source inverter in the energy storage converter control framework includes a parallel voltage and frequency error droop loop connected to the phase-locked loop current-source inverter, comprising: Based on the current topology of the energy storage converter, the output current, output voltage and load current of the energy storage converter are collected. The DQ components, angular frequency, and phase angle of the microgrid voltage are obtained through a generalized second-order integral DSOGI software phase-locked loop and PARK transform. Based on the phase angle, the output current and load current DQ components are obtained through a synchronous coordinate system; Based on the obtained microgrid voltage angular frequency, the difference between the angular frequency and the system rated angular frequency is used to obtain the D-axis current command of the energy storage converter current loop through the frequency active control loop. The voltage amplitude is obtained from the DQ component of the obtained microgrid voltage. The Q-axis current command of the energy storage converter current loop is obtained through the voltage reactive current control loop based on the difference between the system rated voltage and the microgrid voltage amplitude. The current-source voltage and frequency error droop loop of the phase-locked loop current-source inverter in the energy storage converter control framework further includes: Obtain the active and reactive power output of the diesel generator; The current command of the energy storage converter current loop is obtained based on the load current DQ component, the given active power output of the diesel generator, and the reactive power. The DQ-axis reference current command of the energy storage converter current loop is obtained by adding the obtained current command of the energy storage converter and the DQ-axis current command after passing through a first-order inertial filter.

2. The control method for parallel connection of an energy storage converter and a generator set to resist impact loads according to claim 1, characterized in that, The establishment of an energy storage converter control framework based on the current topology of the energy storage converter and the rotating coordinate system DQ-axis voltage and current control method includes: Based on the current topology of the energy storage converter, the output current, output voltage and load current of the energy storage converter are collected; The DQ components, angular frequency, and phase angle of the microgrid voltage are obtained through a generalized second-order integral DSOGI software phase-locked loop and PARK transform. The output current and load current DQ components are obtained based on the phase angle via a synchronous coordinate system.

3. The control method for parallel connection of an energy storage converter and a generator set to resist impact loads according to claim 2, characterized in that, The method of establishing a control framework for an energy storage converter based on the current topology of the energy storage converter and the voltage and current control method of the rotating coordinate system DQ axis also includes: Obtain the active and reactive power output of the diesel generator; The current command of the energy storage converter current loop is obtained based on the load current DQ component, the given active power output of the diesel generator, and the reactive power.

4. The control method for parallel connection of an energy storage converter and a generator set to resist impact loads according to claim 3, characterized in that: The active and reactive power output of the diesel generator is 0.75 times the economic power, i.e., the rated power, of the diesel generator unit.

5. The control method for parallel connection of an energy storage converter and a generator set to resist impact loads according to claim 1, characterized in that, The control of the energy storage converter via SVPWM modulation strategy after the current loop includes: Based on the current topology of the energy storage converter, the output current, output voltage and load current of the energy storage converter are collected. The DQ components, angular frequency, and phase angle of the microgrid voltage are obtained through a generalized second-order integral DSOGI software phase-locked loop and PARK transform. Based on the phase angle, the output current and load current DQ components are obtained through a synchronous coordinate system; Based on the obtained microgrid voltage angular frequency, the difference between the angular frequency and the system rated angular frequency is used to obtain the D-axis current command of the energy storage converter current loop through the frequency active control loop. The voltage amplitude is obtained from the DQ component of the obtained microgrid voltage. The Q-axis current command of the energy storage converter current loop is obtained through the voltage reactive current control loop based on the difference between the system rated voltage and the microgrid voltage amplitude. Obtain the active and reactive power output of the diesel generator; The current command of the energy storage converter current loop is obtained based on the load current DQ component, the given active power output of the diesel generator, and the reactive power. The DQ-axis reference current command of the energy storage converter current loop is obtained by adding the obtained current command of the energy storage converter and the DQ-axis current command after passing through a first-order inertial filter. The control signal is obtained by using the current control equation based on the acquired DQ axis reference current command and output current.

6. The control method for parallel connection of an energy storage converter and a generator set to resist impact loads according to claim 5, characterized in that, The control of the energy storage converter via SVPWM modulation strategy after the current loop also includes: Based on the phase angle between the control signal and the microgrid voltage, the PWM control signal of the energy storage converter switching transistor is obtained through inverse coordinate transformation and SVPWM modulation. The operation of the energy storage converter is controlled based on the PWM control signal.

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