CN104079008B - A kind of method of supplying power to based on micro-capacitance sensor and electric power system - Google Patents

Abstract

The invention discloses a power supply method and a power supply system based on a microgrid. The system includes a clean energy power generation system (100), a microgrid, and an AC load (400) located in a power supply area. The microgrid includes a plurality of VF source energy storage converters (200), and the VF source energy storage converters (200) in parallel and controlled by the VF source energy storage converters (200). A plurality of PQ source energy storage converters (300). The VF source energy storage converter (200) is used to supply power to the AC load (400) connected to the microgrid when the current total demand power of the AC load (400) does not exceed its actual maximum output power. The plurality of PQ source energy storage converters are selected to be turned on by the VF source energy storage converters (200) respectively when the current total demand power of the AC load (400) exceeds its actual maximum output power, so as to build a capacity-expanded The microgrid supplies power to AC loads (400). The invention can improve the operation stability of the power supply system and prolong the service life of the PQ source energy storage converter.

Description

A kind of power supply method and power supply system based on microgrid

technical field

The invention relates to the technical field of power grids, and more specifically, to a power supply method and power supply system based on a microgrid.

Background technique

In the existing technology, in order to effectively solve the problem of power supply for users in areas without electricity, the usual solution in the industry is to construct a micro-grid through the parallel connection of multiple VF source energy storage converters in areas without electricity, and through the constructed micro The grid supplies electricity to users in areas without electricity.

The above-mentioned micro-grid constructed by the parallel connection of VF source energy storage converters can only be satisfied by increasing the number of parallel units or increasing the capacity of single VF source energy storage converters when the capacity demand is increasing. However, the method of expanding the capacity of the microgrid by unilaterally increasing the number or capacity of parallel VF source energy storage converters is subject to technical limitations (at present, there are certain restrictions on increasing the number of parallel units or increasing the capacity), that is, the microgrid The design capacity of the power grid is limited, which cannot meet the requirements of centralized power supply for large user groups in areas without electricity (such as remote counties and islands).

Contents of the invention

The technical problem to be solved by the present invention is to provide a power supply method and power supply system based on a microgrid in view of the above-mentioned defects of the prior art.

The technical solution adopted by the present invention to solve the technical problem is: construct a power supply method based on a microgrid, the microgrid includes a plurality of VF source energy storage converters and a plurality of PQ source energy storage converters connected in parallel; The method comprises the steps of:

S1) Start all VF source energy storage converters in the microgrid, and supply power to AC loads connected to the microgrid through the VF source energy storage converters;

S2) When the current total demand power of the AC load exceeds the actual maximum output power of the VF source energy storage converter, turn on one or more PQ sources in the microgrid through the VF source energy storage converter The energy storage converter expands the capacity of the microgrid, and provides centralized power supply to the AC loads in the power supply area through the expanded microgrid;

Each of the PQ source energy storage converters has at least one second PCS unit, and each VF source energy storage converter has at least one first PCS unit; the following steps are also included before the step S1:

S0) pre-store the ID numbers of all the second PCS units of all PQ source energy storage converters in each first PCS unit of the VF source energy storage converters, and designate one among all the first PCS units as Main PCS unit; the main PCS unit is used for power allocation between the VF source energy storage converter where the main PCS unit is located and the multiple PQ source energy storage converters, and according to the power allocation result The multiple PQ source energy storage converters are used for on/off control.

In the above microgrid-based power supply method of the present invention, the step S2 further includes: the main PCS unit first calculates the actual maximum output power of the VF source energy storage converter, and then converts the VF source energy storage converter to Compare the actual maximum output power of the inverter with the current total demand power of the AC load in the power supply area;

Wherein, P _VFoutput = W*P _VF ; P _VFoutput is the actual maximum output power of the VF source energy storage converter, and W is the percentage of the actual maximum output power and the rated output power of the VF source energy storage converter , P _VF is the rated output power of the VF source energy storage converter;

If the main PCS unit judges that the current total demand power of the AC load does not exceed the actual maximum output power of the VF source energy storage converter, return to step S1.

In the above-mentioned microgrid-based power supply method of the present invention, the step of the VF source energy storage converter in the step S2 turning on one or more PQ source energy storage converters in the microgrid to expand the microgrid includes: :

S21) The main PCS unit calculates the number X of PQ source energy storage converters to be turned on in the microgrid through a preset power distribution algorithm;

S22) The main PCS unit randomly selects an X group of second PCS unit ID numbers from among its pre-stored multiple groups of second PCS unit ID numbers, and sends an X group of second PCS unit ID numbers corresponding to the X group of second PCS unit ID numbers. Part or all of the second PCS units in the unit issue a power-on command to turn on X PQ source energy storage converters including the X group of second PCS units;

S23) The X PQ source energy storage converters and the VF source energy storage converters connected in parallel together constitute a microgrid whose maximum output power can reach the current total power demand of the AC loads in the power supply area.

In the above-mentioned microgrid-based power supply method of the present invention, the power distribution algorithm used to calculate the number X of PQ source energy storage converters to be turned on in the step S21 is as follows:

X=(P _demandpower- η*m*a*P _pcs1 )/(η*b*P _pcs2 ); where,

P _demandpower is the current total demand power of the AC load in the power supply area;

m is the number of VF source energy storage converters in the microgrid;

a is the number of first PCS units included in the VF source energy storage converter;

P _PCS1 is the rated output power of the first PCS unit;

η is the percentage interval between the actual output power and the rated output power acceptable to the microgrid;

b is the number of second PCS units included in the PQ source energy storage converter;

P _PCS2 is the rated output power of the second PCS unit.

In the above microgrid-based power supply method of the present invention, the step S2 further includes: judging whether the main PCS unit fails and when the main PCS unit fails, the VF source energy storage converter Select any first PCS unit except the master PCS unit from all the included first PCS units, and designate the first PCS unit as a new master PCS unit to replace the failed original master PCS unit.

In the above-mentioned microgrid-based power supply method of the present invention, the following steps are also included after the step S2:

S3) When the current total demand power of the AC load drops by at least one output power of the second PCS unit, calculate the number X′ of PQ source energy storage converters that need to be shut down according to the power distribution algorithm. Randomly select X′ PQ source energy storage converters from the source energy storage converters, and instruct part or all of the second PCS units of the X′ PQ source energy storage converters to perform shutdown operations.

The present invention also constructs a power supply system based on a micro-grid, the system includes a clean energy power generation system, a micro-grid, and an AC load located in the power supply area, and the micro-grid includes a plurality of VF source energy storage converters, and The VF source energy storage converters are connected in parallel and controlled by multiple PQ source energy storage converters of the VF source energy storage converters;

The VF source energy storage converter is used to supply power to the AC load connected to the microgrid when the current total demand power of the AC load does not exceed its actual maximum output power;

The plurality of PQ source energy storage converters are selected to be turned on by the VF source energy storage converters respectively when the current total demand power of the AC load exceeds the actual maximum output power of the VF source energy storage converters, so as to form an expanded The microgrid supplies AC loads;

Each of the VF source energy storage converters includes a group of parallel first PCS units, and each of the PQ source energy storage converters includes a group of parallel second PCS units;

The first PCS unit includes a main PCS unit, and the main PCS unit includes a main controller, a first rectifier electrically connected to the main controller, a first inverter and a first storage battery;

Each of the second PCS units includes a slave controller, a second rectifier electrically connected to the slave controller, a second inverter, and a second storage battery;

The master controller is configured to send a start-up instruction to at least one of the slave controllers when the current total demand power of the AC load exceeds the actual maximum output power of the VF source energy storage converter;

The main controller is also used to judge that when the power difference between the maximum output power of the expanded microgrid and the current total demand power of the AC load reaches or exceeds the output power of at least one of the second PCS units, send to at least one One of the slave controllers sends a shutdown command;

The slave controller is configured to turn on/off the second PCS unit where the slave controller is located when receiving the start-up/shutdown instruction of the master controller.

In the above-mentioned power supply system based on the microgrid of the present invention, the communication mode between the VF source energy storage converter and each of the PQ source energy storage converters includes RS485, Ethernet, CAN bus, PLC, and ZigBee.

Since the power supply method and power supply system based on the microgrid of the present invention adopt the method of increasing the number of PQ source energy storage converters connected in parallel with the VF source energy storage converter and controlled by the VF source energy storage converter The technical solution of infinite capacity expansion overcomes the limitation of unilaterally increasing the number or capacity of VF source energy storage converters in the prior art to expand the capacity of the microgrid, and realizes the infinite expansion of the capacity of the microgrid. The purpose of automatic adjustment of output power, improving the stability of power supply system operation, reducing power consumption of power supply system, and prolonging the service life of PQ source energy storage converter.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is the first kind of structure diagram of the power supply system based on the microgrid provided by the preferred embodiment of the present invention;

Fig. 2 is a second schematic structural diagram of a power supply system based on a microgrid provided by a preferred embodiment of the present invention;

Fig. 3 is a structural block diagram of the main PCS unit/any first PCS unit of the microgrid-based power supply system shown in Fig. 1 or Fig. 2;

Fig. 4 is the structural block diagram of any second PCS unit of the power supply system based on the microgrid shown in Fig. 1 or Fig. 2;

Fig. 5 is a flowchart of a microgrid-based power supply method provided by a preferred embodiment of the present invention.

detailed description

In order to solve the defect in the prior art that the way of unilaterally increasing the number or capacity of VF source energy storage converters 200 to expand the microgrid is limited, the main innovations of the present invention are: 1) by adding The number of energy storage converters 200 connected in parallel and controlled by the number of PQ source energy storage converters 300 of the VF source energy storage converter 200 can expand the microgrid infinitely; 2) the main power in the VF source energy storage converter 200 The PCS unit 201 can perform flexible power distribution between the VF source energy storage converter 200 where the PCS unit 201 is located and multiple PQ source energy storage converters 300 according to the change of the total power demand of the AC load 400 in the power supply area According to the output power allocation quota of the PQ source energy storage converter 300, some PQ source energy storage converters 300 are correspondingly turned on or off, so as to reduce system power consumption and realize maximum utilization of system resources.

Since the present invention adopts the design of unlimited expansion of the microgrid by increasing the number of PQ source energy storage converters 300 connected in parallel with the VF source energy storage converter 200 and controlled by the VF source energy storage converter 200, It solves the technical problem that the way of expanding the capacity of the microgrid by unilaterally increasing the number or capacity of the VF source energy storage converter 200 in the prior art is limited, and realizes the infinite expansion of the capacity of the microgrid and the automatic output power of the microgrid. regulation, as well as improving the stability of the power supply system, reducing the power consumption of the power supply system, and prolonging the service life of the PQ source energy storage converter 300 .

In order to make the purpose of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in FIG. 1 , the microgrid-based power supply system of the present invention includes a clean energy power generation system 100 , a microgrid connected to the clean energy power generation system 100 through an AC busbar, and an AC load 400 located in a power supply area. The microgrid includes multiple VF source energy storage converters 200, and multiple PQ source energy storage converters connected in parallel with the multiple VF source energy storage converters and controlled by one of the VF source energy storage converters device 300. Each VF source energy storage converter 200 includes several first PCS (Power Conversion System) units with the same specifications (battery capacity, output power), and each PQ source energy storage converter 300 includes several specifications ( The second PCS (Power Conversion System) unit with the same battery capacity and output power). The communication methods between the multiple VF source energy storage converters 200 and the multiple PQ source energy storage converters 300 include RS485, Ethernet, CAN bus and PLC (PowerLine Communication).

The clean energy power generation system 100 is used to charge the VF source energy storage converter 200 and multiple PQ source energy storage converters 300 in the microgrid.

The VF source energy storage converter 200 is used to supply power to the AC load 400 connected to the microgrid when the current total demand power of the AC load 400 does not exceed its actual maximum output power;

The multiple PQ source energy storage converters 300 are respectively selected to be turned on by the VF source energy storage converter 200 when the current total demand power of the AC load 400 reaches or exceeds its actual maximum output power, so as to construct an expanded microgrid. The AC load 400 supplies power.

Among them, P _VFoutput = w*P _VF ; P _VFoutput = the actual maximum output power of the VF source energy storage converter 200, P _VF is the rated output power of the VF source energy storage converter 200, and W is the VF source energy storage The percentage of the actual maximum output power of the converter 200 to the rated output power.

The difference between the microgrid-based power supply system shown in FIG. 2 of the present invention and the microgrid-based power supply system shown in FIG. The advantage of using ZigBee short-range wireless communication technology is that it overcomes the problem of complex internal wiring of the micro-grid, greatly reduces the use of cables, and reduces the incidence of fire accidents in the micro-grid.

As shown in FIG. 3 , any one of the multiple VF source energy storage converters 200 designates one of the first PCS units 201 as the main PCS unit 201 . The main PCS unit 201 is used to perform power distribution between the VF source energy storage converter 200 where it is located and multiple PQ source energy storage converters 300, and to convert the multiple PQ source energy storage converters according to the power distribution results The device 300 performs switch control.

In the present invention, if the operation of the main PCS unit 201 fails, the VF source energy storage converter 200 where the main PCS unit is located randomly selects all first PCS units 201 other than the main PCS unit 201 Any one of the first PCS units 201 is designated as the new main PCS unit 201 to replace the original main PCS unit 201 that has failed, so as to ensure the safe and stable operation of the power supply system.

The main PCS unit 201 includes a main controller 2011 , a first rectifier 2012 electrically connected to the main controller 2011 , a first inverter 2013 and a first storage battery 2014 .

As shown in FIG. 4 , each second PCS unit 301 includes a slave controller 3011 , a second rectifier 3012 electrically connected to the slave controller 3011 , a second inverter 3013 and a second battery 3014 .

The first rectifier 2012/second rectifier 3012 is used to convert the alternating current from the clean energy power generation system 100 into direct current and then input it to the first storage battery 2014/second storage battery 3014 for storage. Both the first inverter 2013 and the second inverter 3013 are used to convert the DC power provided by the battery into AC power and then deliver it to the AC load 400 through the AC bus.

The main controller 2011 is used to calculate the number of PQ source energy storage converters 300 to be turned on through a power distribution algorithm when the current total demand power of the AC load 400 exceeds the maximum output power of the VF source energy storage converter 200, And send a power-on command to each slave controller 3011 of the second PCS unit 301 of the same number. The multiple slave controllers 3011 are configured to respectively perform a boot operation on the multiple second PCS units 301 where the multiple slave controllers 3011 are located when receiving a boot command from the master controller 2011 .

The main controller 2011 is also used to calculate the number of PQ source energy storage converters 300 that need to be shut down through a power distribution algorithm when the current total demand power of the AC load 400 drops at least one output power of the second PCS unit 301, And send a shutdown command to each slave controller 3011 of the second PCS unit 301 of the same number. The plurality of slave controllers 3011 are configured to respectively perform shutdown operations on the plurality of second PCS units 301 where the plurality of slave controllers 3011 are located when receiving a shutdown command from the master controller 2011 .

The derivation process of the above-mentioned power allocation algorithm of the present invention is as follows:

Based on the energy conversion relationship between the microgrid and the AC load 400, the following equation (1) can be obtained from the energy conservation law: P _demandpower = η*(m*a*P _pcs1 +X*b*P _pcs2 );

Solving equation (1) can get: X=(P _demandpower- η*m*a*P _pcs1 )/(η*b*P _pcs2 ), which is the power distribution algorithm formula of the present invention; Wherein,

P _demandpower is the current total demand power of the AC load 400 in the power supply area;

m is the number of VF source energy storage converters in the microgrid;

X is the number of PQ source energy storage converters 300 to be turned on;

a is the number of first PCS units 201 included in the VF source energy storage converter 200;

P _PCS1 is the rated output power of the first PCS unit 201;

η is the percentage interval between the acceptable actual output power and the rated output power of the microgrid;

b is the number of first PCS units 201 included in the PQ source energy storage converter 300;

P _PCS2 is the rated output power of the second PCS unit 301 .

In a preferred implementation of the microgrid-based power supply system of the present invention, the range of η is (75%, 85%), and the value of W is 80%. Multiple VF source energy storage converters 200 and multiple PQ source energy storage converters 300 in the microgrid "reserve" a part of the electric energy. A power transmission failure to ensure the continuous normal operation of the entire power supply system.

The following will take the preferred implementation mode of the present invention as an example to illustrate the power supply method based on the microgrid of the present invention:

As shown in Figure 5, in step S101, the administrator of the power supply system based on the microgrid of the present invention pre-sets the 4 second PCS units 301 (output power is 500KW) included in each PQ source energy storage converter 300 The ID number is stored in the 4 first PCS units 201 (output power is 250KW) of the VF source energy storage converter 200, and one of the 4 first PCS units 201 is designated to implement the VF source energy storage converter The main PCS unit 201 for power distribution tasks between 200 and multiple PQ source energy storage converters 300 and the on/off control of multiple PQ source energy storage converters 300 .

In step S102, the manager of the power supply system based on the microgrid first turns on the VF source energy storage converter 200, and supplies power to the AC load 400 connected to the microgrid through the VF source energy storage converter 200.

In step S103, if the main PCS unit 201 in the VF source energy storage converter 200 judges that the current total demand power of the AC load 400 does not exceed the maximum output power (i.e. 1MW) of the VF source energy storage converter 200, then return Step S102 ; if the main PCS unit 201 judges that the current total demand power of the AC load 400 has exceeded the maximum output power of the VF source energy storage converter 200 , execute the next step S104 .

In step S104, the main PCS unit 201 calculates the number of PQ source energy storage converters 300 to be turned on according to its built-in power distribution formula.

Example: Suppose η = 80%, P _demandpower = 10MW, P _PCS1 = 250KW, P _PCS2 = 500KW, the main PCS unit 201 can calculate X︰6 according to the above-mentioned various data and power distribution algorithm formula, which is the PQ source to be turned on The number of energy storage converters 300 is six.

In step S105, the main PCS unit 201 randomly selects 6 sets of second PCS unit ID numbers from the multiple sets of pre-stored second PCS unit ID numbers in it, and sends to the 6 sets of second PCS unit ID numbers corresponding to the 6 sets of second PCS unit ID numbers. The PCS unit 301 issues a power-on command at the same time. The six groups of second PCS units 301 respectively receive the above-mentioned boot command and execute the boot operation through their respective slave controllers 3011 .

In step S106, the 6 PQ source energy storage converters 300 composed of the above 6 groups of second PCS units 301 are turned on and the VF source energy storage converters 200 connected in parallel with them form an expanded microgrid as the AC load in the power supply area 400 power supply.

In step S107, if the main PCS unit 201 judges that the current total demand power drop of the AC load 400 does not exceed 500KW, maintain the number of power-on of the PQ source energy storage converter 300, and return to step S106; if the main PCS unit 201 When it is judged that the drop value of the current total demand power of the AC load 400 exceeds 500KW, the next step S108 is executed.

In step S108, the main PCS unit 201 calculates the number of PQ source energy storage converters 300 that need to be shut down through the power distribution algorithm, so as to reduce the output power of the microgrid accordingly, and reduce the power consumption of the power supply system based on the microgrid, Ensure the safety of power supply in the power supply area and prolong the service life of PQ source energy storage equipment.

Assuming that the current total demand power of the AC load 400 in the power supply area drops to 8KW, the main PCS unit 201 can calculate that the number of PQ source energy storage converters 300 that need to be shut down is one according to the above power distribution formula of the present invention.

In step S109, the main PCS unit 201 searches for 6 groups of second PCS unit ID numbers corresponding to the above-mentioned 6 PQ source energy storage converters 300, and randomly selects a group of second PCS unit ID numbers among the 6 groups of second PCS unit ID numbers. PCS unit ID number, send a shutdown command to the 4 second PCS units 301 corresponding to the group of second PCS unit ID numbers, to shut down the PQ source energy storage converter 300 composed of the 4 second PCS units 301 . After the PQ source energy storage converter 300 enters the shutdown state, return to step S103.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (8)

1. A microgrid-based power supply method is characterized in that the microgrid comprises a plurality of VF source energy storage converters (200) and a plurality of PQ source energy storage converters (300) which are connected in parallel; the method comprises the following steps:

s1) starting all VF source energy storage converters (200) in the microgrid, and supplying power to an alternating current load (400) connected to the microgrid through the VF source energy storage converters (200);

s2) when the current total required power of the alternating current load (400) exceeds the actual maximum output power of the VF source energy storage converter, starting one or more PQ source energy storage converters (300) in a microgrid through the VF source energy storage converter (200) to expand the microgrid, and supplying power to the alternating current load (400) in a power supply area in a centralized manner through the expanded microgrid;

each said PQ source energy storage converter (300) has at least one second PCS unit (301) and each VF source energy storage converter (200) has at least one first PCS unit (201); the method further comprises the following steps before the step S1:

s0) the ID numbers of all second PCS units (301) of all PQ source energy storage converters (300) are prestored in each first PCS unit (201) of the VF source energy storage converter (200), and one of all first PCS units (201) is designated as a main PCS unit (201); the main PCS unit is used for distributing power between the VF source energy storage converter (200) where the main PCS unit (201) is located and the PQ source energy storage converters (300) and controlling the PQ source energy storage converters (300) to be turned on and turned off according to power distribution results.

2. The microgrid-based power supply method of claim 1, wherein the step S2 further comprises: the main PCS unit (201) calculates the actual maximum output power of the VF source energy storage converter (200) firstly, and then compares the actual maximum output power of the VF source energy storage converter (200) with the current total required power of an alternating current load (400) in a power supply area;

wherein, P_VFoutput＝W*P_VF；P_VFoutputThe actual maximum output power of the VF source energy storage converter (200) is obtained, W is the percentage of the actual maximum output power to the rated output power of the VF source energy storage converter (200), and P is_VFRated output power of the VF source energy storage converter (200);

and if the main PCS unit (201) judges that the current total required power of the alternating current load (400) does not exceed the actual maximum output power of the VF source energy storage converter (200), returning to the step S1.

3. The microgrid-based power supply method of claim 2, wherein the step of enabling the VF source energy storage converter (200) to turn on one or more PQ source energy storage converters (300) in the microgrid to expand the microgrid in step S2 comprises:

s21), the main PCS unit (201) calculates the number X of PQ source energy storage converters (300) needing to be started in the microgrid through a preset power distribution algorithm;

s22) the main PCS unit (201) randomly selects X groups of second PCS unit ID numbers from a plurality of groups of prestored second PCS unit ID numbers, and sends a starting-up instruction to part or all of the X groups of second PCS units (301) corresponding to the X groups of second PCS unit ID numbers so as to start X PQ source energy storage converters (300) containing the X groups of second PCS units (301);

s23), the X PQ source energy storage converters (300) and the VF source energy storage converter (200) connected in parallel form a micro-grid of which the maximum output power can reach the current total required power of an alternating current load (400) in a power supply area.

4. The microgrid-based power supply method of claim 3, characterized in that the power distribution algorithm used in step S21 for calculating the number X of PQ source energy storage converters (300) to be turned on is as follows:

X＝(P_demandpower-η*m*a*P_pcs1)/(η*b*P_pcs2) (ii) a Wherein,

P_demandpower-the current total required power of the ac loads (400) of the power supply area;

m is the number of VF source energy storage converters in the microgrid;

a is the number of first PCS units (201) contained in the VF source energy storage converter (200);

P_PCS1is the rated output power of the first PCS unit (201);

eta is the percentage interval range of the actual output power and the rated output power which can be accepted by the micro-grid;

b is the number of second PCS units (301) contained in the PQ source energy storage converter (300);

P_PCS2is the sum of the second PCS unit (301)And (4) determining the output power.

5. The microgrid-based power supply method of claim 4, wherein the step S2 further comprises: and judging whether the main PCS unit (201) has a fault or not, when the main PCS unit (201) has a fault, selecting any one of the first PCS units (201) except the main PCS unit (201) from all the first PCS units (201) contained in the VF source energy storage converter (200), and designating the first PCS unit (201) as a new main PCS unit (201) to replace the original main PCS unit (201) with the fault.

6. The microgrid-based power supply method of claim 5, characterized by further comprising the following steps after the step S2:

s3) when the current total required power of the alternating current load (400) is reduced by the output power of at least one second PCS unit (301), calculating the number X ' of PQ source energy storage converters (300) to be shut down according to a power distribution algorithm, randomly selecting X ' PQ source energy storage converters (300) from the X started PQ source energy storage converters (300), and instructing part or all second PCS units (301) of the X ' PQ source energy storage converters (300) to perform shut-down operation.

7. A micro-grid based power supply system is characterized by comprising a clean energy power generation system (100), a micro-grid and an alternating current load (400) located in a power supply area, wherein the micro-grid comprises a plurality of VF source energy storage converters (200) and a plurality of PQ source energy storage converters (300) which are connected with the VF source energy storage converters (200) in parallel and controlled by the VF source energy storage converters (200);

the VF source energy storage converter (200) is used for supplying power to an alternating current load (400) connected to the microgrid when the current total required power of the alternating current load (400) does not exceed the actual maximum output power;

the PQ source energy storage converters (300) are respectively selectively started by the VF source energy storage converter (200) when the current total required power of the alternating current load (400) exceeds the actual maximum output power of the VF source energy storage converter (200), so that a capacity-expanded microgrid is formed to supply power to the alternating current load (400);

each VF source energy storage converter (200) comprises a set of first PCS units (201) connected in parallel, and each PQ source energy storage converter (300) comprises a set of second PCS units (301) connected in parallel;

the first PCS unit (201) comprises a main PCS unit (201), and the main PCS unit (201) comprises a main controller (2011), a first rectifier (2012) electrically connected with the main controller (2011), a first inverter (2013) and a first storage battery (2014);

each second PCS unit (301) comprises a slave controller (3011), a second rectifier (3012) electrically connected with the slave controller (3011), a second inverter (3013) and a second storage battery (3014);

the master controller (2011) is used for sending a starting command to at least one slave controller (3011) when the current total required power of an alternating current load (400) exceeds the actual maximum output power of the VF source energy storage converter (200);

the master controller (2011) is further configured to send a shutdown instruction to the at least one slave controller (3011) when a power difference between the maximum output power of the expanded microgrid and the current total required power of the alternating-current load (400) reaches or exceeds the output power of the at least one second PCS unit (301);

the slave controller (3011) is configured to turn on/off the second PCS unit (301) in which the slave controller is located when receiving a power on/off instruction from the master controller (2011).

8. The microgrid-based power supply system of claim 7, characterized in that the communication modes between the VF source energy storage converter (200) and each PQ source energy storage converter (300) include RS485, Ethernet, CAN bus, PLC, and ZigBee.