# US 2020/0287410 A1 · Microgrid control system and microgrid

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- Number: US 2020/0287410 A1
- Document ID: US20200287410A1
- Status: Published application
- Kind: A1
- Application number: 16/764,865
- Filed: 2018-04-08
- Published: 2020-09-10
- Earliest claimed: 2017-12-28
- Assignees: Beijing Etechwin Electric Co., Ltd.
- Applicants: Beijing Etechwin Electric Co., Ltd.
- Inventors: Shuaiyang Zhao; Yunhai Lan; Chengzhi Qin
- Web page: https://patentgrep.com/patent/US20200287410A1

## CPC

- H02J 13/16: the power network being controlled at grid-level, e.g. using aggregators
- G05B 11/36: with provision for obtaining particular characteristics, e.g. proportional, integral, differential
- H02H 1/0007: {concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445)}
- H02H 7/28: for meshed systems
- H02J 3/01: Arrangements for reducing harmonics or ripples
- H02J 3/18: Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J 3/32: using batteries or super capacitors with converting means
- H02J 3/42: with automatic parallel connection when synchronisation is achieved
- H02J 3/44: with means for ensuring correct phase sequence
- H02J 13/1323: {using optical fibres}
- H02J 13/14: the power network being locally controlled, e.g. home energy management systems [HEMS]
- H02J 3/381: {Dispersed generators}
- H02J 2103/35: Grid-level management of power transmission or distribution systems, e.g. load flow analysis or active network management
- H02J 2105/10: Local stationary networks having a local or delimited stationary reach
- Y02E 40/30: Reactive power compensation
- Y02E 40/70: Smart grids as climate change mitigation technology in the energy generation sector
- Y02E 60/00: Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02P 80/14: District level solutions, i.e. local energy networks
- Y04S 10/12: Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation
- Y04S 10/22: Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units
- Y04S 40/124: using wired telecommunication networks or data transmission busses
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS

## Abstract

Provided in the present invention are a microgrid control system and a microgrid, the microgrid control system comprising: a grid-connected switch, an energy router, a first controller and a second controller; the first controller controls the grid-connected switch and sends a first control instruction; the second controller receives the first control instruction and responds to the first control instruction for controlling the energy router.

## Claims

### Claim 1

A control system of a microgrid, comprising: a grid-connection switch, an energy router, a first controller and a second controller,
wherein the first controller controls connection and disconnection of the grid-connection switch and sends a first control instruction based on a state of the control system of the microgrid; and
the second controller receives the first control instruction from the first controller and controls the energy router in response to the first control instruction.

### Claim 2 (depends on 1)

The control system of the microgrid according to claim 1, wherein
in a case that the grid-connection switch is disconnected, the first controller generates a first frequency regulation instruction and a first voltage regulation instruction based on an actual voltage and an actual frequency of a power grid, determines a first active power instruction and a first reactive power instruction based on a three-phase voltage of the power grid and a three-phase voltage of the microgrid, and takes the first frequency regulation instruction, the first voltage regulation instruction, the first active power instruction and the first reactive power instruction as the first control instruction, and
wherein the second controller is in a VSG control mode.

### Claim 3 (depends on 2)

The control system of the microgrid according to claim 2, wherein
the first controller determines a voltage amplitude of the power grid and an angular frequency of the power grid, and takes the voltage amplitude of the power grid as the first voltage regulation instruction and takes the angular frequency of the power grid as the first frequency regulation instruction; and
the second controller receives the first voltage regulation instruction and the first frequency regulation instruction, and controls the energy router in response to the first voltage regulation instruction and the first frequency regulation instruction, to make a voltage amplitude and a frequency outputted by the microgrid consistent with the voltage amplitude and the frequency outputted by the power grid.

### Claim 4 (depends on 2)

The control system of the microgrid according to claim 2, wherein
the first controller determines a frequency of the power grid, a voltage amplitude of the power grid, a frequency of the microgrid and a voltage amplitude of the microgrid; performs PI adjustment on a difference between the frequency of the power grid and the frequency of the micro-grid, and determines the difference after the PI adjustment as the first active power instruction; and performs PI adjustment on a difference between the voltage amplitude of the power grid and the voltage amplitude of the microgrid, and determines the difference after the PI adjustment as the first reactive power instruction; and
the second controller receives the first active power instruction and the first reactive power instruction, and controls the energy router in response to the first active power instruction and the first reactive power instruction, to make the energy router output an active power and a reactive power that match a load.

### Claim 5 (depends on 2)

The control system of the microgrid according to claim 2, wherein
the second controller determines an actual output active power and an actual output reactive power based on an output voltage of the energy router, and determines angles of positive sequence rotation coordinate transformation and negative sequence rotation coordinate transformation of the output voltage and an output current of the energy router by invoking a rotor motion equation and a prime mover regulation equation in combination with the actual output active power, the first active power instruction and the first frequency regulation instruction; and
the second controller determines d axis component given value and q axis component given value of a positive sequence output voltage of the energy router based on the actual output reactive power, the first reactive power instruction and the first voltage regulation instruction, and sets d axis component given value and q axis component given value of a negative sequence output voltage of the energy route as zero.

### Claim 6 (depends on 5)

The control system of the microgrid according to claim 5, wherein the second controller is configured to:
perform positive sequence rotation coordinate transformation and negative sequence rotation coordinate transformation on the output voltage of the energy router, to obtain a positive sequence component and a negative sequence component of the output voltage;
obtain direct current components of the positive sequence component and the negative sequence component of the output voltage by a notch filter;
perform positive sequence rotation coordinate transformation and negative sequence rotation coordinate transformation on the output current of the energy router, to obtain a positive sequence component and a negative sequence component of the output current;
obtain direct current components of the positive sequence component and the negative sequence component of the output current by a notch filter;
calculate an instantaneous active power and an instantaneous reactive power of the energy router based on the direct current components of the positive sequence component and the negative sequence component of the output voltage and the direct current components of the positive sequence component and the negative sequence component of the output current; and
pass the instantaneous active power and the instantaneous reactive power through a low pass filter to obtain the actual output active power and the actual output reactive power.

### Claim 7 (depends on 6)

The control system of the microgrid according to claim 6, wherein the second controller is further configured to:
perform PI adjustment on differences between the d axis component given value and the q axis component given value of the positive sequence output voltage and the negative sequence output voltage of the energy router and the direct current components of the positive sequence component and the negative sequence component of the output voltage, and takes the differences after the PI adjustment as a positive sequence output current component given value and a negative sequence output current component given value of the energy router; and
determine a positive sequence output voltage component given value and a negative sequence output voltage component given value of the energy router in a static coordinate system based on the differences between the positive sequence output current component given value and the negative sequence output current component given value of the energy router and the direct current components of the positive sequence component and the negative sequence component of the output current after PI adjustment, to realize dual closed loop control of voltage and current.

### Claim 8 (depends on 7)

The control system of the microgrid according to claim 7, wherein
the second controller detects odd harmonics in the output voltage of the energy router, and determines a direct current component of each of the harmonic voltages, perform PI adjustment on a difference between the direct current component of each of the harmonic voltages and zero, and perform inverse transformation on the difference after the PI adjustment to obtain a given value of each of the harmonic voltages.

### Claim 9 (depends on 8)

The control system of the microgrid according to claim 8, wherein
the second controller obtains a feedforward amount of the output voltage by performing a static coordinate transformation on the output voltage of the energy router, and generates a modulated wave by invoking an SVPWM modulation wave generation function in combination with a sum of the positive sequence output voltage component given value and the negative sequence output voltage component given value in the static coordinate system, the given value of each of the harmonic voltages and the feedforward amount of the output voltage, to control operation of the energy router.

### Claim 10 (depends on 5)

The control system of the microgrid according to claim 5, wherein
the second controller adds the first voltage regulation instruction to an output of a reactive power deviation regulation by invoking a ramp function.

### Claim 11 (depends on 1)

The control system of the microgrid according to claim 1, wherein
in a case that the grid-connection switch is disconnected, the first controller determines a voltage amplitude of a power grid, a voltage phase of the power grid, a voltage phase of the microgrid and an angular frequency of the microgrid, and detects whether a difference between the voltage phase of the power grid and the voltage phase of the microgrid reaches a predetermined threshold; and
the first controller controls the grid-connection switch to be connected if detecting that the difference reaches the predetermined threshold.

### Claim 12 (depends on 11)

The control system of the microgrid according to claim 11, wherein
the first controller superimposes a predetermined multiple of the difference onto the angular frequency of the microgrid to obtain a second frequency regulation instruction, and takes the voltage amplitude of the power grid as the second voltage regulation instruction, and further determines a second active power instruction and a second reactive power instruction that match a load, and then takes the second frequency regulation instruction, the second voltage regulation instruction, the second active power instruction and the second reactive power instruction as the first control instruction.

### Claim 13 (depends on 1)

The control system of the microgrid according to claim 1, wherein
in a case that the grid-connection switch is connected, the first controller generates a third active power instruction and a third reactive power instruction, as the first control instruction, based on a power of a load and a state of an energy storage unit; and
wherein the second controller is in a PQ control mode.

### Claim 14 (depends on 13)

The control system of the microgrid according to claim 13, wherein
the second controller determines a positive sequence output voltage component given value and a negative sequence output voltage component given value in a static coordinate system based on a positive sequence output current component given value and a negative sequence output current component given value of the energy router and direct current components of a positive sequence component and a negative sequence component of an output current of the energy router, and generates a modulated wave by invoking an SVPWM modulation wave generation function in combination with a sum of a positive sequence output voltage component given value and a negative sequence output voltage component given value in the static coordinate system and a feedforward amount of an output voltage of the energy router, to control operation of the energy router.

### Claim 15 (depends on 1)

The control system of the microgrid according to claim 1, wherein
in a case that the grid-connection switch is connected, the first controller controls the grid-connection switch to be disconnected if detecting that a current flowing through the grid-connection switch reaches a predetermined current threshold.

### Claim 16 (depends on 15)

The control system of the microgrid according to claim 15, wherein
the first controller generates a fourth active power instruction and a fourth reactive power instruction according to the current flowing through the grid-connection switch, and then takes the fourth active power instruction and the fourth reactive power instruction as the first control instruction.

### Claim 17 (depends on 1)

The control system of the microgrid according to claim 1, wherein
the first controller controls the grid-connection switch to be disconnected if detecting a power grid fault under a grid-connected state of the control system of the microgrid.

### Claim 18 (depends on 1)

The control system of the microgrid according to claim 1, wherein
the second controller comprises a digital signal processor, and
wherein the second controller is configured to be in a VSG control mode when the digital signal processor runs a VSG algorithm and be in a PQ control mode when the digital signal processor runs a PQ algorithm.

### Claim 19 (depends on 1)

A microgrid, comprising: the control system of the microgrid according to claim 1, an energy storage unit and a load, wherein
the energy storage unit is connected to an end of the energy router, and the other end of the energy router is connected to a power grid via the grid-connection switch; the energy router supplies power to the load;
the energy storage unit and the grid-connection switch are connected to the first controller via an optical network;
the energy router is connected to the second controller via an optical network, and the second controller is connected to the first controller via an optical network;
in a case that the microgrid system is in an off-grid state, the control system of the microgrid converts a direct current of the energy storage unit into an alternating current, for supplying to the load; and
in a case that the microgrid system is in a grid-connected state, the control system of the microgrid converts an alternating current of the power grid into a direct current, for charging the energy storage unit.