Parallel control method for maneuvering micro-grid and diesel power station

Abstract

The invention relates to a parallel control method for a maneuvering micro-grid and a diesel power station, which comprises the following steps of: in a power supply network formed by connecting alternating current sides of the maneuvering micro-grid and the diesel power station in parallel, obtaining PCS alternating current frequency and voltage change through sampling, and respectively calculating PCS output active power and reactive power which need to be adjusted by applying an anti-droop algorithm; through rapid adjustment of the PCS in a millisecond-level control period, rapid load power sharing of the maneuvering micro-grid and the diesel power station is realized, the load sharing adjustment time of the power supply network during sudden load change is greatly shortened, the pressure of the diesel power station for coping with sudden load change is reduced, the service life of equipment is prolonged, and the system reliability and the electric energy quality are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrids, and in particular to a parallel control method of a mobile microgrid and a diesel power station. Background Art

[0002] In areas where the power grid cannot cover electricity consumption, such as military field training, emergency rescue, etc., diesel power stations are traditionally widely used for independent power supply. With the development of distributed power generation systems such as photovoltaic and wind power generation, mobile microgrids have been developed on the basis of fixed microgrids to meet the needs of transportation and mobile power supply, becoming a powerful supplement to diesel power stations.

[0003] Limited by factors such as cost and mobile transportation, the capacity of mobile microgrids or diesel power stations is generally not large. During use, the load power is often large, which requires the power supply equipment to be able to supply power in parallel to increase the power supply capacity. Due to the different power generation characteristics of diesel power stations and mobile microgrids, parallel power supply has always been a problem. At present, diesel power stations and mobile microgrids are generally powered independently. On the one hand, it will cause a large capacity margin for each power supply unit and waste resources; on the other hand, it also limits the application and development of mobile microgrids. Only by solving the problem of parallel connection of diesel power stations and mobile microgrids can mobile microgrids be widely used and developed.

[0004] The mobile microgrid is connected in parallel with the diesel power station for power supply. The common method is to use the diesel engine as a voltage source and the mobile microgrid as a current source for power supply. The EMS inside the mobile microgrid controls the external power output of the mobile microgrid according to the load changes. Since the EMS needs to perform data acquisition, equipment communication and control processes, the entire process needs to be calculated in seconds, so the response speed of the mobile microgrid is in seconds, and it is impossible to achieve real-time response in milliseconds. When the load suddenly changes, it is entirely up to the diesel power station to deal with the load mutation, and it is impossible to achieve true parallel operation. This method can be used for occasions where the load changes little; when the load suddenly changes or changes greatly, especially when it exceeds the rated output power of the diesel power station, it is easy to cause the diesel power station to overload protection, and long-term use accelerates the damage of the diesel power station.

[0005] Another way is that the power conversion unit in the mobile microgrid adopts the form of a virtual synchronous machine to simulate the power generation process of the synchronous generator, so that its characteristics are consistent with the output characteristics of the diesel power station, thereby achieving parallel operation. The disadvantages of this method are obvious. First, the virtual synchronous machine algorithm is extremely complex, and the algorithm and hardware requirements are very high. It is currently immature and has few practical applications. Second, the virtual synchronous machine algorithm is not universal. When connected in parallel with a diesel power station, it is adapted according to the characteristics of the diesel power station's synchronous generator, and it is impossible to connect different diesel power stations in parallel.

[0006] The PCS control frequency of the mobile microgrid is generally between 30k and 6k, that is, the control cycle is 33us to 167us. When the PCS is incorporated into the diesel power station, the constant power mode is adopted, and the control algorithm samples the dual-loop control, that is, the outer loop is the power loop PI regulator, and the inner loop is the current loop PI regulator. The power regulation speed is in milliseconds. According to the "GB 34120-2017 Technical Specifications for Electrochemical Energy Storage System Converters", the conversion time from full-power charging to full-power discharging of the PCS is no more than 100ms. That is, for a PCS with a rated power of 100kW, the conversion from 100kW charging to 100kW discharging does not exceed 100ms. Since the EMS of the mobile microgrid needs to perform data acquisition, equipment communication and control processes, the entire process needs to be calculated in seconds, so the response speed of the mobile microgrid is in seconds. Summary of the invention

[0007] In view of the above analysis, an embodiment of the present invention aims to provide a parallel control method for a mobile microgrid and a diesel power station, so as to solve the problem that when the mobile microgrid and the diesel power station are connected in parallel for power supply, once the load suddenly changes, the changed power is borne entirely by the diesel power station, the power balancing adjustment time is long, and it is easy to cause losses to the diesel power station.

[0008] On the one hand, an embodiment of the present invention provides a parallel control method for a mobile microgrid and a diesel power station. The mobile microgrid and the AC side of the diesel power station are connected in parallel to form a power supply network. During operation, the power output is periodically adjusted by the PCS in the mobile microgrid. The following steps are performed in each cycle:

[0009] Based on the PCS output AC voltage and AC current sampling values, calculate the AC bus AC frequency, and PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback;

[0010] Based on the AC bus AC frequency, PCS AC active voltage and reactive voltage, the anti-droop algorithm is used to calculate the active power droop setting and reactive power droop setting;

[0011] Based on the active power droop setting and reactive power droop setting, the active power setting and reactive power setting issued are used to calculate the active power expectation and reactive power expectation;

[0012] Perform limit control on the expected active power and the expected reactive power;

[0013] Calculating active power deviation and reactive power deviation based on the expected active power and reactive power after limit control;

[0014] Power output is adjusted based on the active power deviation and the reactive power deviation.

[0015] Based on the further improvement of the above method, the AC bus AC frequency, and the PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback are calculated based on the PCS output AC voltage and AC current sampling values. The process is as follows:

[0016] Sample the PCS output AC voltage and AC current.

[0017] Based on the PCS output AC voltage, the phase-locked loop algorithm is used to calculate the AC bus frequency, PCS active voltage and reactive voltage.

[0018] Based on the PCS output AC current, the PCS active current and reactive current are calculated by applying abc-dq transformation.

[0019] The PCS active power feedback is calculated based on the PCS active voltage and active current, and the reactive power feedback is calculated based on the PCS reactive voltage and reactive current.

[0020] Based on the further improvement of the above method, the anti-droop algorithm is applied to calculate the active power droop setting and the reactive power droop setting based on the AC bus AC frequency, PCS AC active voltage, and reactive voltage, including:

[0021] Pg=-kf×(fms-f 0 )+P 0 , where

[0022] Pg is the active power droop setting,

[0023] P 0 is the PCS active power reference,

[0024] fms is the AC bus AC frequency,

[0025] f 0 is the PCS frequency reference value,

[0026] kf is the frequency-active power droop coefficient;

[0027] Qg=-kv×(Vms-V 0 )+Q 0 , where

[0028] Qg is the reactive power droop given,

[0029] Q 0 is the PCS reactive power benchmark,

[0030] Vms is the AC bus voltage,

[0031] V 0 is the PCS voltage reference value,

[0032] kv is the voltage-reactive power droop coefficient.

[0033] Based on the further improvement of the above method, the frequency-active power droop coefficient is expressed as the following formula:

[0034] In the formula,

[0035] fmin is the minimum AC frequency set for PCS, and Pmax is the maximum active power set for PCS.

[0036] Based on the further improvement of the above method, the voltage-reactive power droop coefficient is expressed as the following formula:

[0037] In the formula,

[0038] Qmax is the maximum reactive power set for PCS, and Vmin is the minimum AC frequency set for PCS.

[0039] Based on the further improvement of the above method, the calculation of the expected active power and the expected reactive power is specifically as follows:

[0040] Pset1=Pset+Pg, where Pset is the AC active power given by the sender.

[0041] Qset1=Qset+Qg, where Qset is the AC reactive power reference issued.

[0042] Based on the further improvement of the above method, the limiting control of the expected active power and the expected reactive power includes:

[0043] If the expected active power is greater than the maximum active power, the expected active power is set equal to the maximum active power;

[0044] If the desired reactive power is greater than the maximum reactive power, the desired reactive power is set equal to the maximum reactive power.

[0045] Based on the further improvement of the above method, the active power deviation and the reactive power deviation are calculated, and the active power deviation and the reactive power deviation are calculated as follows:

[0046] deltaP=Pset1-Pms, where Pms is the PCS active power feedback,

[0047] deltaQ=Qset1-Qms, where Qms is the PCS reactive power feedback.

[0048] Based on the further improvement of the above method, the power output is adjusted by respectively connecting the active power deviation and the reactive power deviation to the active power regulator and the reactive power regulator to calculate the duty cycle, outputting the control signal to the drive circuit for signal amplification, and then outputting it to the power conversion unit to control the adjusted power output.

[0049] Another aspect of the present invention discloses a power grid system in which a mobile microgrid and a diesel power station are connected in parallel and can quickly respond to sudden load changes, comprising:

[0050] Diesel power stations, operating as AC voltage sources;

[0051] Mobile microgrid, including electronic conversion unit PCS, microgrid energy management system EMS and energy storage system,

[0052] Among them, the mobile microgrid is connected to the AC bus as an AC current source through the PCS, connected in parallel with the diesel power station, and the power output is adjusted periodically in microseconds in the following way:

[0053] Based on the PCS output AC voltage and AC current sampling values, calculate the AC bus AC frequency, and PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback;

[0054] Based on the AC bus AC frequency, PCS AC active voltage and reactive voltage, the anti-droop algorithm is used to calculate the active power droop setting and reactive power droop setting;

[0055] Based on the active power droop setting and reactive power droop setting, the active power setting and reactive power setting issued are used to calculate the active power expectation and reactive power expectation;

[0056] Perform limit control on the expected active power and the expected reactive power;

[0057] Calculating active power deviation and reactive power deviation based on the expected active power and reactive power after limit control;

[0058] Power output is adjusted based on the active power deviation and the reactive power deviation.

[0059] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0060] 1. The frequency-active power and voltage-reactive power anti-droop control algorithm adopted in the present invention calculates the active power and reactive power given by AC voltage and AC frequency as the control given of traditional PQ control. The parallel control of the mobile microgrid and the diesel power station gives full play to the PCS response speed advantage through algorithm control, shortening the original second-level regulation to microsecond-level regulation, so that the steady-state and transient mobile microgrid and diesel power station can realize rapid power balancing, thereby improving system reliability and power quality.

[0061] 2. The present invention does not require any modification to the parallel power supply network structure of the mobile microgrid and the diesel power station, nor does it require the addition of additional sampling circuits. By integrating an original algorithm in the PCS, various values ​​can be obtained based on preset parameters and the existing power grid to quickly calculate the PCS power deviation. It can be integrated into various PCSs and applied to the parallel power grid scenarios of mobile microgrids and diesel power stations.

[0062] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components;

[0064] Figure 1 It is a schematic diagram of the power supply network of the mobile microgrid and the diesel motor in parallel;

[0065] Figure 2 This is the structure diagram of the mobile microgrid;

[0066] Figure 3 It is a schematic diagram of the anti-droop parallel control of PCS in the parallel power supply network of the mobile microgrid and the diesel power station;

[0067] Figure 4 The control flow chart of the PCS anti-droop algorithm for the mobile microgrid and the diesel power station AC side parallel power supply. DETAILED DESCRIPTION

[0068] To facilitate understanding, the relevant concepts involved in the cloud computing environment are first explained.

[0069] 1. Microgrid: In this article, microgrid refers to a distributed small power grid constructed by multiple energy sources such as wind power generation units, photovoltaic power generation units, internal combustion engine generator sets, energy storage batteries, fuel cells, etc., including grid-connected microgrids and off-grid microgrids.

[0070] 2. Mobile microgrid: refers to a microgrid device that is mobile and can be transferred by people, vehicles, etc. to meet the demand for mobile power supply. It is generally equipped with energy storage system, power conversion unit and EMS, and can choose distributed power generation systems such as photovoltaic power generation system and wind power generation system.

[0071] 3. Power conversion unit: The power conversion unit in this article is the key equipment for power conversion in the microgrid. For AC power supply, it refers to PCS, which is generally called energy storage converter, energy storage inverter, etc. PCS control mode is generally divided into constant power mode (P / Q mode, P represents active power, Q represents reactive power) and constant voltage mode (V / F mode, V represents voltage, F represents frequency). When the mobile microgrid is connected to the diesel power station, the PCS adopts the constant power mode; when the mobile microgrid is independently powered, the PCS works in the constant voltage mode, establishes the industrial frequency voltage and frequency (AC220V / 50HzV or AC380V / 50Hz), and independently supplies power to the AC load.

[0072] 4. EMS: refers to the microgrid energy management system, which is a software and hardware system used for coordinated control and energy management of multiple distributed power sources within a microgrid.

[0073] 5. Diesel power station: A diesel power station refers to a generator that uses a diesel engine as the motive force and an AC synchronous generator to generate electricity and output 220V / 230V or 380V / 400V with an industrial frequency of 50Hz. It can also be called a diesel generator set.

[0074] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0075] A specific embodiment of the present invention discloses a parallel control method for a mobile microgrid and a diesel power station. The mobile microgrid and the AC side of the diesel power station are connected in parallel to form a power supply network. During operation, the power output is periodically adjusted by the PCS in the mobile microgrid. The following steps are performed in each cycle:

[0076] Based on the PCS output AC voltage and AC current sampling values, calculate the AC bus AC frequency, and PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback;

[0077] Based on the AC bus AC frequency, PCS AC active voltage and reactive voltage, the anti-droop algorithm is used to calculate the active power droop setting and reactive power droop setting;

[0078] Based on the active power droop setting and reactive power droop setting, the active power setting and reactive power setting issued are used to calculate the active power expectation and reactive power expectation;

[0079] Perform limit control on the expected active power and the expected reactive power;

[0080] Calculating active power deviation and reactive power deviation based on the expected active power and reactive power after limit control;

[0081] Power output is adjusted based on the active power deviation and the reactive power deviation.

[0082] Specifically, Figure 1 As shown, the mobile microgrid and the diesel power station are connected in parallel to form a power grid to supply power to the load.

[0083] like Figure 2 As shown, the mobile microgrid structure in this embodiment includes an electronic conversion unit PCS, a microgrid energy management system EMS and an energy storage system, wherein the mobile microgrid PCS is connected to the AC bus as an AC current source and is connected in parallel with the diesel power station.

[0084] Specifically, a mobile microgrid is generally internally configured with an energy storage system, a power conversion unit PCS and an EMS. Preferably, a distributed power generation system such as a photovoltaic power generation system and a wind power generation system is used. The energy storage system is connected to the DC input side of the power conversion unit PCS, and the AC output side of the PCS supplies power to the outside and is connected to the AC bus. The distributed power generation system can be connected to the DC side or the AC side of the PCS.

[0085] Figure 3 The schematic diagram of the parallel control network structure of the power supply network composed of the mobile microgrid and the AC side of the diesel power station in parallel is shown, in which the frequency-active power and voltage-reactive power anti-droop control method is applied by PCS.

[0086] Specifically, the rated power of the mobile microgrid is expressed as Pmg_e, the rated power of the diesel power station is expressed as Pgen_e, the load active power is expressed as Pload, and the reactive power is expressed as Qload.

[0087] The mobile microgrid and the diesel power station jointly supply power to a load that is no greater than the sum of their rated powers, that is, Pload≤Pmg_e+Pgen_e.

[0088] The AC active power set received by the mobile microgrid PCS is expressed as Pset, and the reactive power set is expressed as Qset.

[0089] The mobile microgrid EMS sends Pset and Qset to the mobile microgrid PCS with a control period Ts of seconds.

[0090] The AC power setting can come from the host computer instruction or be determined by the EMS according to the load power.

[0091] The control period Ts of the mobile microgrid EMS is in the order of seconds, and the control period Tms of the PCS as an actuator is in the order of microseconds.

[0092] The active power of AC load is expressed as Pload, and the reactive power is expressed as Qload.

[0093] The active power feedback of the mobile microgrid is expressed as Pms, and the reactive power feedback is expressed as Qms.

[0094] In steady state, Pms=Pset, Qms=Qset.

[0095] As a voltage source, the diesel power station automatically maintains the stability of AC voltage and AC frequency.

[0096] According to the law of conservation of energy, the AC active power of a diesel power station is expressed as Pgen=Pload-Pmg, and the reactive power is expressed as Qgen=Qload-Qmg.

[0097] In this embodiment, Figure 4 As shown in FIG. 1 , the process of controlling the parallel power supply of the mobile microgrid and the AC side of the diesel power station through the PCS anti-droop algorithm includes:

[0098] Step S1: Based on the PCS output AC voltage and AC current sampling values, calculate the AC bus AC frequency, and the PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback.

[0099] Furthermore, based on the PCS output AC voltage and AC current sampling values, the AC bus AC frequency, and the PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback are calculated, and the process is:

[0100] Sample the PCS output AC voltage and AC current.

[0101] Based on the PCS output AC voltage, the phase-locked loop algorithm is used to calculate the AC bus frequency, PCS active voltage and reactive voltage.

[0102] Based on the PCS output AC current, the PCS active current and reactive current are calculated by applying abc-dq transformation.

[0103] The PCS active power feedback is calculated based on the PCS active voltage and active current, and the reactive power feedback is calculated based on the PCS reactive voltage and reactive current.

[0104] Specifically, the AC bus AC frequency fms, PCS (active) d-axis voltage ud, and (reactive) q-axis voltage uq are calculated according to the collected AC voltage according to the phase-locked loop algorithm; based on the collected AC current, the PCS (active) d-axis current id and (reactive) q-axis current iq are calculated according to the abc-dq transformation.

[0105] Preferably, the PCS active power feedback Pms and reactive power feedback Qms are in accordance with the following formula:

[0106] Pms=ud×id+uq×iq;

[0107] Qms=uq×id-ud×iq.

[0108] Step S2: Based on the AC bus AC frequency, PCS AC active voltage, and reactive voltage, an anti-droop algorithm is applied to calculate the active power droop setting and the reactive power droop setting.

[0109] Furthermore, the calculation of the active power droop setting and the reactive power droop setting by applying the anti-droop algorithm based on the AC bus AC frequency, the PCS AC active voltage, and the reactive voltage includes:

[0110] Pg=-kf×(fms-f 0 )+P 0 , where

[0111] Pg is the active power droop setting,

[0112] P 0 is the PCS active power reference,

[0113] fms is the AC bus AC frequency,

[0114] f 0 is the PCS frequency reference value,

[0115] kf is the frequency-active power droop coefficient;

[0116] Qg=-kv×(Vms-V 0 )+Q 0 , where

[0117] Qg is the reactive power droop given,

[0118] Q 0 is the PCS reactive power benchmark,

[0119] Vms is the AC bus voltage,

[0120] V 0 is the PCS voltage reference value,

[0121] kv is the voltage-reactive power droop coefficient.

[0122] Furthermore, the frequency-active power droop coefficient is expressed as the following formula:

[0123] In the formula,

[0124] fmin is the minimum AC frequency set for PCS, and Pmax is the maximum active power set for PCS.

[0125] Furthermore, the voltage-reactive power droop coefficient is expressed as the following formula:

[0126] In the formula,

[0127] Qmax is the maximum reactive power set for PCS, and Vmin is the minimum AC frequency set for PCS.

[0128] Step S3: Calculate the expected active power and the expected reactive power based on the active power droop setting and the reactive power droop setting, the sampled active power setting and the reactive power setting.

[0129] Furthermore, the calculation of the expected active power and the expected reactive power is specifically as follows:

[0130] Pset1=Pset+Pg, where Pset is the AC active power given by EMS.

[0131] Qset1=Qset+Qg, where Qset is the AC reactive power reference issued by the EMS.

[0132] Step S4: performing limit control on the expected active power and the expected reactive power.

[0133] Furthermore, the limiting control of the expected active power and the expected reactive power includes:

[0134] If the expected active power is greater than the maximum active power, the expected active power is set equal to the maximum active power;

[0135] If the desired reactive power is greater than the maximum reactive power, the desired reactive power is set equal to the maximum reactive power.

[0136] Step S5: Calculate the active power deviation and reactive power deviation based on the expected active power and reactive power after the limit control.

[0137] Furthermore, the calculation of active power deviation and reactive power deviation is specifically as follows:

[0138] deltaP=Pset1-Pms, where Pms is the PCS active power feedback,

[0139] deltaQ=Qset1-Qms, where Qms is the PCS reactive power feedback.

[0140] Step S6: adjusting the power output based on the active power deviation and the reactive power deviation.

[0141] Furthermore, the power output is regulated by respectively connecting the active power deviation and the reactive power deviation to the active power regulator and the reactive power regulator to calculate the duty cycle, outputting the control signal to the drive circuit for signal amplification, and then outputting it to the power conversion unit to control the regulated power output.

[0142] Specifically, the active power deviation deltaP is connected to the active power regulator, and the reactive power deviation deltaQ is connected to the reactive power regulator to calculate the duty cycle respectively, which is output to the drive circuit for signal amplification and then sent to the power conversion unit to perform energy conversion, that is, the output regulated PCS power.

[0143] Wait for the current control cycle to end and proceed to the next cycle.

[0144] Furthermore, the control period is determined by the PCS control frequency.

[0145] Another embodiment of the present invention discloses a power grid system in which a mobile microgrid and a diesel power station are connected in parallel and can quickly respond to sudden load changes, and is characterized by comprising:

[0146] Diesel power stations, operating as AC voltage sources;

[0147] Mobile microgrid, including electronic conversion unit PCS, microgrid energy management system EMS and energy storage system,

[0148] Among them, the mobile microgrid is connected to the AC bus as an AC current source through the PCS, connected in parallel with the diesel power station, and the power output is adjusted periodically in microseconds in the following way:

[0149] Based on the PCS output AC voltage and AC current sampling values, calculate the AC bus AC frequency, and PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback;

[0150] Based on the AC bus AC frequency, PCS AC active voltage and reactive voltage, the anti-droop algorithm is used to calculate the active power droop setting and reactive power droop setting;

[0151] Based on the active power droop setting and reactive power droop setting, the active power setting and reactive power setting issued are used to calculate the active power expectation and reactive power expectation;

[0152] Perform limit control on the expected active power and the expected reactive power;

[0153] Calculating active power deviation and reactive power deviation based on the expected active power and reactive power after limit control;

[0154] Power output is adjusted based on the active power deviation and the reactive power deviation.

[0155] The following is a specific example of the technical solution of the present invention.

[0156] Diesel power station output rated voltage V 0 Usually 220V / 380V, rated frequency f 0Usually 50Hz. The rated power of the diesel power station is Pgen_e = 50kW, the rated power of the mobile microgrid is Pm_e = 50kW, the EMS control period is Ts = 1s, and the control period of the PCS control algorithm is Tms = 100us. The AC power supply voltage is the three-phase voltage reference V 0 =380V, frequency reference f 0 =50Hz, the maximum apparent power of the load does not exceed 100kVA. The sampled AC bus voltage is represented by Vms, and the AC bus frequency is represented by fms.

[0157] In a certain EMS control cycle, the load power Pload = 40kW, the active power given by the mobile microgrid PCS is Pset = 20kW, and the reactive power given is Qset = 0kvar, then the active power output of the diesel power station is Pgen = 20kW. The maximum output power of PCS is Pmax = 50kW, the minimum AC frequency of PCS output is fmin = 45Hz, and the minimum operating voltage is Vmin = 330V. The PCS voltage reference V is obtained by reading the configuration parameters saved by PCS 0 and frequency reference f 0 , Active power reference P 0 and reactive power reference Q 0 , minimum AC frequency fmin, maximum active power Pmax, maximum reactive power Qmax.

[0158] When a control cycle starts, the following process is performed:

[0159] Step 1: PCS collects PCS AC voltage and AC current through voltage and current sampling circuits, and calculates AC bus AC frequency fms=45Hz, AC bus AC voltage Vms=380V, active power feedback Pms=20kW, and reactive power feedback Qms=0kvar.

[0160] Step 2: Pmax, P 0 、f 0 , fmin, Qmax, Q 0 、V 0 If Vmin and Vmin are known, the frequency-active parameter kf and voltage-reactive parameter kv can be calculated according to the droop control method:

[0161]

[0162]

[0163] Then, the active power droop given Pg and reactive power droop given Qg are calculated as follows:

[0164] Pg=-kf×(fms-f0 )+P 0 =-10.0×(45Hz-50Hz)+0kW=50kW;

[0165] Qg=-kv×(Vms-V 0 )+Q 0 =-10.0×(380V-380V)+0kvar=0kvar;

[0166] The active power droop given by Pg = 50kW, and the reactive power droop given by Qg = 0kvar.

[0167] Step 3: Calculate the expected active power Pset1 and the expected reactive power Qset1, which are:

[0168] Pset1=Pset+Pg=20kW+50kW=70kW;

[0169] Qset1=Qset+Qg=0kvar+0kavr=0kvar.

[0170] Step 4: Then, limit the active power setting:

[0171] Since the expected active power Pset1 = 70kW is greater than the maximum active power Pmax = 50kW, set Pset1 = 50kW;

[0172] The expected reactive power Qset1=0 kvar is less than the maximum reactive power Qmax=50 kvar, so Qset1=0 kvar is set.

[0173] Step 5: Calculate the active power deviation deltaP and reactive power deviation deltaQ respectively:

[0174] deltaP=Pset1-Pms=50kW-20kW=30kW;

[0175] deltaQ=Qset1-Qms=0kvar-0kvar=0kvar.

[0176] Step 6: Connect the active power deviation deltaP to the active power regulator and the reactive power deviation deltaQ to the reactive power regulator to calculate the duty cycle respectively, output it to the drive circuit for signal amplification, and then send it to the power conversion unit to perform energy conversion, that is, output the adjusted PCS power.

[0177] In this example, the PCS control frequency is 10kHz, so 100us is set as the unit control cycle length. After each 100us timing is over, the next control cycle is started and all steps are repeated.

[0178] It should be noted that the output regulated PCS power is automatically adjusted by the power regulator according to preset parameters. Specifically, the duty cycle is calculated by the P / Q control method, and the control level signal is output. After the signal is amplified by the driving circuit, it is sent to the power conversion unit to output the regulated PCS power value. Due to the working principle and characteristics of the power regulator, the regulated PCS power value can only be estimated, but the power value curve adjusted in each control cycle generally presents a gradual adjustment and gradually slowing process, so that the mobile microgrid and the diesel generator set can gradually adapt to the power change and finally realize load power balancing. Since the present invention uses PCS as the control subject to achieve regulation, the control cycle is shortened to milliseconds. Referring to the national standard for the PCS control cycle, in this embodiment, it is estimated that 10ms can achieve power load balancing between the mobile microgrid and the diesel motor.

[0179] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0180] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A parallel control method for a mobile microgrid and a diesel power station, characterized in that: The mobile microgrid is connected in parallel with the AC side of the diesel power station to form a power supply network. During operation, the PCS in the mobile microgrid periodically adjusts the power output and performs the following steps in each cycle: Based on the PCS output AC voltage and AC current sampling values, calculate the AC bus AC frequency, and PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback; Based on the AC bus AC frequency, PCS AC active voltage and reactive voltage, the anti-droop algorithm is used to calculate the active power droop setting and reactive power droop setting; Based on the active power droop setting and reactive power droop setting, the active power setting and reactive power setting issued are used to calculate the active power expectation and reactive power expectation; Perform limit control on the expected active power and the expected reactive power; Calculating active power deviation and reactive power deviation based on the expected active power and reactive power after limit control; Power output is adjusted based on the active power deviation and the reactive power deviation.

2. A parallel control method for a mobile microgrid and a diesel power station according to claim 1, characterized in that: The process of calculating the AC bus AC frequency, the PCS AC active voltage, the PCS AC reactive voltage, the PCS AC active power feedback, and the PCS reactive power feedback is as follows: Sample the PCS output AC voltage and AC current. Based on the PCS output AC voltage, the phase-locked loop algorithm is used to calculate the AC bus frequency, PCS active voltage and reactive voltage. Based on the PCS output AC current, the PCS active current and reactive current are calculated by applying abc-dq transformation. The PCS active power feedback is calculated based on the PCS active voltage and active current, and the reactive power feedback is calculated based on the PCS reactive voltage and reactive current.

3. A parallel control method of a mobile microgrid and a diesel power station according to claim 2, characterized in that: The method of calculating the active power droop setting and the reactive power droop setting based on the AC bus AC frequency, the PCS AC active voltage, and the reactive voltage by applying the anti-droop algorithm includes: Pg=-kf×(fms-f0)+P0, where Pg is the active power droop setting, P0 is the PCS active power reference, fms is the AC bus AC frequency, f0 is the PCS frequency reference value, kf is the frequency-active power droop coefficient; Qg=-kv×(Vms-V0)+Q0, where: Qg is the reactive power droop given, Q0 is the PCS reactive power reference, Vms is the AC bus voltage, V0 is the PCS voltage reference value, kv is the voltage-reactive power droop coefficient.

4. A parallel control method for a mobile microgrid and a diesel power station according to claim 3, characterized in that: The frequency-active power droop coefficient is expressed as the following formula: In the formula, fmin is the minimum AC frequency set for PCS, and Pmax is the maximum active power set for PCS.

5. The parallel control method of a mobile microgrid and a diesel power station according to claim 3 is characterized in that: The voltage-reactive power droop coefficient is expressed as the following formula: In the formula, Qmax is the maximum reactive power set for PCS, and Vmin is the minimum AC frequency set for PCS.

6. A parallel control method for a mobile microgrid and a diesel power station according to any one of claims 4 and 5, characterized in that: The calculation of the expected active power and the expected reactive power is specifically as follows: Pset1=Pset+Pg, where Pset is the AC active power given by the sender. Qset1=Qset+Qg, where Qset is the AC reactive power reference issued.

7. A parallel control method for a mobile microgrid and a diesel power station according to claim 6, characterized in that: The limiting control of the expected active power and the expected reactive power includes: If the expected active power is greater than the maximum active power, the expected active power is set equal to the maximum active power; If the desired reactive power is greater than the maximum reactive power, the desired reactive power is set equal to the maximum reactive power.

8. A parallel control method for a mobile microgrid and a diesel power station according to claim 7, characterized in that: The calculation of active power deviation and reactive power deviation is specifically as follows: deltaP=Pset1-Pms, where Pms is the PCS active power feedback, deltaQ=Qset1-Qms, where Qms is the PCS reactive power feedback.

9. A parallel control method of a mobile microgrid and a diesel power station according to claim 8, characterized in that: The power output is regulated by respectively connecting the active power deviation and the reactive power deviation to the active power regulator and the reactive power regulator to calculate the duty cycle, outputting the control signal to the drive circuit for signal amplification, and then outputting it to the power conversion unit to control the regulated power output.

10. A power grid system in which a mobile microgrid and a diesel power station are connected in parallel and can quickly respond to sudden load changes, characterized in that: include: Diesel power stations, operating as AC voltage sources; Mobile microgrid, including electronic conversion unit PCS, microgrid energy management system EMS and energy storage system, Among them, the mobile microgrid is connected to the AC bus as an AC current source through the PCS, connected in parallel with the diesel power station, and the power output is adjusted periodically in microseconds in the following way: Based on the PCS output AC voltage and AC current sampling values, calculate the AC bus AC frequency, and PCS AC active voltage, reactive voltage, active power feedback, and reactive power feedback; Based on the AC bus AC frequency, PCS AC active voltage and reactive voltage, the anti-droop algorithm is used to calculate the active power droop setting and reactive power droop setting; Based on the active power droop setting and reactive power droop setting, the active power setting and reactive power setting issued are used to calculate the active power expectation and reactive power expectation; Perform limit control on the expected active power and the expected reactive power; Calculating active power deviation and reactive power deviation based on the expected active power and reactive power after limit control; Power output is adjusted based on the active power deviation and the reactive power deviation.

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