Content
The Power Plant Controller offers intelligent and flexible solutions for the control of all PV power plants in the megawatt range. It is suitable for PV power plants with central inverters as well as for PV systems with decentralized string inverters.
With the help of simulation tools, valuable predictions on the behavior of the Power Plant Controller and the design of the system are possible even before the commissioning of a PV power plant.
A high performance PLC enables fast adaptation of reactive and active power in accordance with the requirements of
Technical Information
POWER PLANT CONTROLLER
1 Power Plant Controller SMA Solar Technology AG
1 Power Plant Controller 1.1 System Overview
The Power Plant Controller assumes control of the entire PV power plant. The PV power plant can combine both central inverters and decentralized string inverters, which are monitored and controlled by the Cluster Controller or Inverter Manager.
Figure 1: Principle of signal transfer in a PV power plant with Power Plant Controller
In the Power Plant Controller, the setpoints for grid management services are received and compared with the values measured at the point of interconnection. Based on this comparison, the Power Plant Controller calculates the required output values which it transmits to the central inverters and the Cluster Controllers or Inverter Managers. Up to
200 central inverters or a maximum of 20 SMA Cluster Controllers and/or Inverter Managers can be connected. In master/slave operation of multiple Power Plant Controllers, uniform control of up to 1,000 central inverters is possible (see Section 3.9, page 9).
The Power Plant Controller can receive setpoints in digital or analog form and via Modbus. The digital setpoints are transmitted by the grid operator or by a higher-level SCADA system.
SMA Solar Technology AG 1 Power Plant Controller
Nearly all international directives for grid management services and all the control procedures described in this document are supported. The Power Plant Controller can read out up to three network analyzers connected to the point of interconnection. The network analyzers can be used for redundancy purposes. For each of the measured values P, Q, V and f, a source can be configured for measured value 1 (default) and for measured value 2 (redundant value). If the source for the measured value 1 fails, the second (redundant) measured value will be used instead.
Transmission of the output values from the Power Plant Controller to central inverters, SMA Cluster Controllers and Inverter Managers takes place via Modbus protocol.
1.2 Design of the Power Plant Controller
Figure 2: Exterior and interior view of the Power Plant Controller (example)
1.3 Dimensions of the Power Plant Controller
Position Designation
A Touch display*
* optional
B Control unit
C Connection area
Width Height Depth Weight
720 mm 1,125 mm 325 mm 60 kg
2 Mounting Information SMA Solar Technology AG
2 Mounting Information 2.1 Minimum Clearances
Observe the following minimum clearances to ensure trouble-free installation.
Observe the minimum clearances to ensure easy mounting, opening and closing of the Power Plant Controller.
The opening angle of the door is 180°.
Figure 3: Minimum Clearances
2.2 Requirements for Mounting
Requirements for the Mounting Location
☐ The Power Plant Controller without display is suitable for outdoor mounting.
☐ The Power Plant Controller with display is only suitable for indoor mounting.
☐ The mounting location must not be in a living or office area.
☐ The mounting location must not block any escape routes.
☐ The mounting location must be freely and safely accessible at all times without the necessity for any auxiliary equipment.
Non-fulfillment of these criteria may restrict servicing.
☐ The mounting location and the mounting foundation must be suitable for the weight and dimensions of the Power Plant Controller.
☐ The ambient conditions must be suitable for the operation of the Power Plant Controller.
☐ The mounting location should not be exposed to direct solar irradiation.
☐ The Power Plant Controller must be mounted on a solid support surface.
SMA Solar Technology AG 2 Mounting Information Permitted Mounting Positions
Figure 4: Permitted mounting position
2.3 Requirements for Commissioning the Power Plant Controller
Since the Power Plant Controller will take over the control of the entire system according to system-specific specifications, it is necessary for the PV power plant to meet the following requirements at the time of commissioning the
Power Plant Controller:
☐ All connected inverters have been commissioned and are feeding electric current into the utility grid.
☐ A network is installed and all central inverters and the SMA Cluster Controller can be reached via port 80 (HTTP) and port 502 (Modbus TCP/UDP).
☐ Local network access to the system network is available.
☐ The current feed-in data can be measured at the grid-connection point by up to two network analyzers or with analog signals. It must be possible to measure the values for active and reactive power, frequency and line-to-neutral voltage of the energy fed in.
☐ The network analyzers must be accessible via the system network.
☐ Commissioning requires sufficient irradiation. The weather forecast should be considered during scheduling.
The behavior of the entire PV system is constantly monitored in the course of commissioning. Consequently, it might be necessary to adjust the parameters of the inverters.
Prior to commissioning, the requirements for the acceptance tests must be agreed upon with the grid operator and SMA Solar Technology AG. This might result in further requirements for commissioning.
The Power Plant Controller can only be reached externally via a VPN connection. SMA must have a VPN connection to the system to be able to intervene promptly whenever service is required.
This VPN connection must not necessarily be permanent, but must be possible for service purposes.
3 Functional Description of the Power Plant Controller SMA Solar Technology AG
3 Functional Description of the Power Plant Controller
3.1 New Functions as of Software Version 01.03.20.R. (Release 3)
• Feed-in limitation (see Section 3.4, page 7)
• Direct marketing interface(see Section 3.4, page 7)
• Individual reactive power supply by the inverters(see Section 3.5, page 7)
• Activation of the functions "Q at Night" and "Q on Demand" in the inverters (see Section 3.5, page 7)
• Disconnection of the inverters(see Section 3.11, page 9)
3.2 Control Procedure
The Power Plant Controller operates with two independent controllers: one active power controller and one reactive power controller. Each controller can be operated in different modes.
All relevant parameters and procedures are configured during commissioning.
It is ensured that all transmitted output values are within the permitted control range for all modes.
The changeover from control or manual mode to control mode is bumpless. This prevents sudden power changes during switchover.
3.3 Control Principle
The actual values of the PV power plant measured at the point of interconnection and the current setpoints are transmitted to the Power Plant Controller. The setpoints can either be specified manually or by the grid operator.
The PID controller in the Power Plant Controller compares the incoming actual values with the setpoints and calculates an output value according to the specifications. The Power Plant Controller transmits this output value to the connected devices. The inverters adjust the power fed in based on the new setpoints and feed this in at the grid-connection point.
There, this power is measured again and transmitted as an actual value to the Power Plant Controller. The new actual values are compared with the setpoints in the PID controller and new output values are calculated that help the inverters achieve the specified setpoints even more closely.
This constant control procedure ensures that changes in the power fed in are monitored and that modified setpoints are taken into account within a very short period of time.
The interval that the Power Plant Controller uses to send the output values to the connected devices must be configured individually for the specific system. A minimum interval of 100 ms is possible for central inverters and a minimum interval of one second for Cluster Controllers. Actual achievable values depend on many factors and must be specified for each system individually.
Mode Description
Control mode The Power Plant Controller transmits the setpoints of the grid operator to the connected devices.
Control mode The Power Plant Controller calculates an output value using the current actual value and the specified setpoint. The actual value is measured in the network analyzer at the point of interconnection.
A deadband can be set up for control within which deviations are ignored and control is not activated.
Manual operation The Power Plant Controller transmits the manually configured setpoint to the connected devices.
The manual setpoint can either be specified via the Modbus protocol or configured via the user interface during commissioning.
SMA Solar Technology AG 3 Functional Description of the Power Plant Controller
3.4 Active Power Control
There are two procedures available for active power control.
Both procedures can operate in parallel with active power control. This ensures that the lower setpoint is transmitted to the connected devices.
If both procedures for active power control are deactivated, the maximum active power setpoint is always active.
Direct Marketing Interface
In addition to the grid operator interface, a direct marketing interface is implemented in the Power Plant Controller.
Alongside the grid operator, the direct marketer can specify direct setpoints for the active power using the Modbus interface. If different default values are specified, the smaller value has priority.
Feed-In Limitation
In some regions, the grid operator requires that the PV energy generated is used exclusively or mostly for
self-consumption. If no active power is allowed to be fed in (zero export), the Power Plant Controller adjusts to a setpoint of 0 W at the feed-in point. To avoid short-term grid feed-in after internal loads have been disconnected, a safety margin can be configured as an offset to the permitted feed-in amount.
3.5 Reactive Power Control
One procedure is active for reactive power control.
Procedure Description
Direct setpoint specification Limitation of the active power setpoint to a setpoint entered on the user interface or to an externally specified setpoint. The permissible range for this setpoint can be parameterized via the user interface.
Setpoint in accordance with
P(f) characteristic curve Frequency-dependent specification of the active power setpoint.
The setpoint is calculated from a characteristic curve. Characteristic curves are available for the requirements in Germany, France, and South Africa.
Procedure Description
Direct setpoint specification Specification of a fixed setpoint for reactive power. The permissible range for this setpoint can be parameterized on the user interface and must not exceed ± 50% of the nominal power of the PV power plant.
Setpoint specification according to Q(V) characteristic curve
Voltage-dependent specification of the reactive power setpoint . The setpoint is calculated from a characteristic curve.
The measured voltage values are smoothed before further processing.
Direct power factor
specification Specification of a fixed power factor to a fixed value within the range.
3 Functional Description of the Power Plant Controller SMA Solar Technology AG
"Q at Night" and "Q on Demand" Function of the Inverters
With the inverter order option "Q at Night" or "Q on Demand", the inverter can supply reactive power in order to stabilize the utility grid during non-feed-in operation, e.g. at night (for further information on the "Q at Night" function, see the inverter manual). By activating the function "Q at Night", the Power Plant Controller can send the reactive power setpoints to the inverter even in non-feed-in mode. This function needs to be activated in the inverter and in the Power Plant Controller under PPC > Grid system services > Device table inverters for each individual inverter.
Individual Reactive Power Supply (2 Options)
There are two options for distributing reactive power to individual inverters:
• via the reactive power limitation for individual inverters
• via activation of the individual reactive power supply It is not possible to use both options simultaneously.
Option 1: Individual reactive power limitation
For this function, the nominal reactive power as well as two possible thresholds are parameterized for each inverter.
If the lower reactive power threshold is reached during operation, the given inverter will not receive any higher output values for the time being. The effectiveness of this threshold is, however, canceled if the inverter would be able
mathematically to supply reactive powers above the second threshold. Using this function, a PV system can, by taking the system topology into account, maintain the power factor required by the grid operator without having to carry out dynamic reduction of the active power. The function is deactivated if both thresholds are set to the same value (default setting).
Option 2: Individual reactive power supply
Alternatively, it is possible to activate the function "Individual reactive power supply". Using this function, inverters with low instantaneous power make a large contribution to reactive power, and vice versa.
3.6 Apparent Power Limitation
The output values of active and reactive power control are limited to the maximum apparent power.
Here, you have the option of configuring priority for active or reactive power.
3.7 Limitation of the Setpoint Modification Gradient
In order to prevent large gradients when modifying the setpoints for active power and reactive power, the gradient for the modifications can be limited by two parameters each: one parameter for increasing the setpoints and one parameter for decreasing the setpoints.
This parameter is independent of the procedure for the smooth transition of the operating modes (see Section 3.2 "Control Procedure", page 6).
3.8 Power Limitation with Strongly Increasing Irradiation Values
In order to prevent a rapid rise in the feed-in power when there is a sudden increase in the irradiation, the power modification can be limited using the function "Limitation of the active power gradient". This function simultaneously activates the function for limiting the gradient of setpoint modification.
SMA Solar Technology AG 3 Functional Description of the Power Plant Controller
3.9 Master/Slave Operation of the Power Plant Controllers
Using Power Plant Controllers, you can monitor a PV power plant with up to 1,000 central inverters.
The master/slave concept of the Power Plant Controllers enables all 1,000 inverters to be controlled uniformly and simultaneously. The Power Plant Controller master transmits the output values for the active and reactive power control to the Power Plant Controller slaves. A Power Plant Controller master can control up to ten Power Plant Controller slaves.
There are three modes of slave operation:
3.10 Temperature and Irradiation Sensors
From release 2.0, you can connect the following sensors to the Power Plant Controller and monitor the measured values of the sensors:
• Two irradiation sensors
• Sensor for the ambient temperature
• Sensor for the temperature of the PV modules
It is possible to receive the measured values via the analog inputs or the Modbus server.
3.11 Disconnection of the Inverters
Fast disconnection of the inverters can be triggered e.g. by the grid operator using a Modbus command. In addition, the active and reactive power setpoint can be set to zero via a digital input.
Slave mode Description
1 The active power setpoints are processed by the controller of the master and transmitted as output values to the slave. The slave does not control but transmits the output values to the inverters.
or
Cascade control: The active power output values of the master are processed by the slave controller as setpoints and sent to the inverters. For this type of slave operation, the slave must receive the actual values from an additional network analyzer. This network analyzer must record the values of the part of the PV power plant that is to be controlled. For cascade control, therefore, an additional network analyzer is required for each slave.
The reactive power setpoints are processed by the slave's own controller.
2 The reactive power setpoints are processed by the controller of the master and transmitted as output values to the slave. The slave does not control but transmits the output values to the inverters.
The active power setpoints are processed by the slave's own controller.
3 The active and reactive power setpoints are processed by the controller of the master and transmitted as output values to the slave. The slave does not control but transmits the output values to the inverters.
4 Interface Description SMA Solar Technology AG
4 Interface Description 4.1 Network Inputs
The Power Plant Controller uses the Modbus protocol for data transmission. The following data can be transmitted by Modbus protocol:
• Specifications of the grid operator to the Power Plant Controller
• Transfer of the output values from the Power Plant Controller to central inverters and SMA Cluster Controllers
• Transfer of internal device data from central inverters and SMA Cluster Controllers to the Power Plant Controller
Figure 5: Principle of the communication network of the PV system with Power Plant Controller (example)
The Power Plant Controller supports the transfer protocols TCP and UDP.
The Power Plant Controller makes two LAN ports available for data transmission by Modbus protocol.
The following are examples for the possible assignment of the network inputs:
For some supported network analyzers it is necessary to put the network analyzer in the network where no inverters are connected. This can be attributed to the communication behavior of the devices.
Input Incoming signals
LAN1 Signals from the transducer, from the central inverters, and the SMA Cluster Controllers LAN3 Specifications of the grid operator
SMA Solar Technology AG 4 Interface Description
4.2 Digital and Analog Inputs
Depending on the order, the Power Plant Controller is equipped with two options for transmitting the analog and digital signals.
It is also possible to connect the I/O components to the Power Plant Controller via the network. This can be coordinated with SMA Solar Technology depending on the project.
Standard Inputs and Outputs
Digital or analog measured data can be transmitted from the network analyzer to the Power Plant Controller via the corresponding inputs. If a feedback signal is requested, it can be transmitted via the associated digital or analog outputs.
Optional Inputs and Outputs
If the inputs and outputs available by default are not sufficient for the requirements of the project, additional inputs and outputs are available via a bus coupler.
As an option, the following inputs and outputs can be used:
4.3 Interfaces
User Interface
The Power Plant Controller can be configured, parameterized and operated with a PC via the network and user interface.
For this, the Chrome or Firefox web browser must be installed on the PC.
Touch Display
Input Description
4 analog inputs for current or 4 analog inputs for voltage
±0 mA to 20 mA, 12 bit resolution or
‒10 V to +10 V, 12 bit resolution
3 analog outputs ±0 mA to 20 mA, 12 bit resolution
6 digital inputs 15 VDC to 30 VDC, typical current consumption: 5 mA
4 digital outputs Power rating: 48 VDC, 30 W
Input Description
8 analog inputs for current or 4 analog inputs for voltage
±0 mA to 20 mA, 12 bit resolution or
‒10 V to +10 V, 12 bit resolution
4 analog outputs Power rating: 250 VAC or 30 VDC, 5 A
12 digital inputs 15 VDC to 30 VDC, typical current consumption: 5 mA
12 digital outputs Power rating: 48 VDC, 30 W
5 Option Code SMA Solar Technology AG
5 Option Code
Code option Option
code Option Explanation
1 - Enclosure 1 Enclosure Enclosure option
2 - Display 0 without display No integrated display
1 With display Switch cabinet equipped with 10.4" TFT touch display (only suitable for indoors)
3 - Voltage supply 0 AC power supply unit,
redundant
(100 VAC to 240 VAC)
For operation on AC supply (100 VAC to 240 VAC)
1 DC power supply unit,
redundant
(30 VDC to 60 VDC)
For operation on DC supply (30 VDC to 60 VDC)
4 - PLC 0 1 control CPU 1 control CPU
5 - Digital outputs 0 4 DO 4 digital outputs on the control CPU,
power rating: 48 VDC/30 W
1 8 DO 4 digital outputs on the control CPU, power
rating: 48 VDC/30 W + 4 digital outputs, power rating: 250 VAC/ or 30 VDC, 5 A
2 12 DO 4 digital outputs on the control CPU, power
rating: 48 VDC/30 W + 8 digital outputs, power rating: 250 VAC/ or 30 VDC, 5 A
3 16 DO 4 digital outputs on the control CPU, power
rating: 48 VDC/30 W + 12 digital outputs, power rating: 250 VAC/ or 30 VDC, 5 A 6 - Digital inputs 0 6 DI 6 digital inputs, signal voltage "1":
15 VDC to 30 VDC, typ. 5 mA current consumption
1 10 DI 10 digital inputs, signal voltage "1":
15 VDC to 30 VDC, typ. 5 mA current consumption
2 14 DI 14 digital inputs, signal voltage "1":
15 VDC to 30 VDC, typ. 5 mA current consumption
3 18 DI 18 digital inputs, signal voltage "1":
15 VDC to 30 VDC, typ. 5 mA current consumption
7 - Analog outputs
(4 mA to 20 mA) 0 3 AO 3 analog outputs, 4 mA to 20 mA,
12 bit resolution
1 5 AO 5 analog outputs, 4 mA to 20 mA,
12 bit resolution
2 7 AO 7 analog outputs, 4 mA to 20 mA,
SMA Solar Technology AG 5 Option Code
8 - Analog inputs 0 4 AI current/voltage 4 analog inputs, 0 V to 10 V or 4 mA to 20 mA, 12 bit resolution
1 4 AI current/voltage
+ 4 AI current 4 analog inputs, 0 V to 10 V or 4 mA to 20 mA, 12 bit resolution + 4 analog inputs, 4 mA to 20 mA, 12 bit resolution
2 4 AI current/voltage
+ 4 AI voltage 4 analog inputs, 0 V to 10 V or
4 mA to 20 mA, 12 bit resolution + 4 analog inputs, ‒10 V to 10 V, 12 bit resolution
3 4 AI current/voltage
+ 8 AI current 4 analog inputs, 0 V to 10 V or
4 mA to 20 mA, 12 bit resolution + 8 analog inputs, 4 mA to 20 mA, 12 bit resolution 9 - Communication
interface 0 None No serial interfaces
10 - Network slot 1 0 None No additional network switch, but with
unmanaged 2-port Fast Ethernet network switch (RJ45, 100 Mbit/s) on the control CPU 1 Network switch 8 TX Unmanaged Fast Ethernet network switch for
industrial networks with 8 copper ports (100 Mbit/s)
2 Network switch 2 FX-M
(SC) 8 TX Unmanaged Fast Ethernet network switch for industrial networks with 8 copper ports and 2 optical fiber ports for multi-mode optical fiber (100 Mbit/s)
3 Network switch 2 FX-S
(SC) 8 TX Unmanaged Fast Ethernet network switch for industrial networks with 8 copper ports and 2 optical fiber ports for single-mode optical fiber (100 Mbit/s)
B Network switch 2 FX-M
(SC) 8 TX MNG Managed Fast Ethernet network switch for industrial networks with 6 RJ45 copper ports and 2 optical fiber ports for multi-mode optical fiber (100 Mbit/s)
C Network switch 2 FX-S
(SC) 8 TX MNG Managed Fast Ethernet network switch for industrial networks with 6 RJ45 copper ports and 2 optical fiber ports for single-mode Code option Option
code Option Explanation
5 Option Code SMA Solar Technology AG
11 - Network slot 2 0 None No additional network switch, but with
unmanaged 2-port Fast Ethernet network switch (RJ45, 100 Mbit/s) on the control CPU 1 Network switch 8 TX Unmanaged Fast Ethernet network switch for
industrial networks with 8 copper ports (100 Mbit/s)
2 Network switch 2 FX-M
(SC) 8 TX Unmanaged Fast Ethernet network switch for industrial networks with 8 copper ports and 2 optical fiber ports for multi-mode optical fiber (100 Mbit/s)
3 Network switch 2 FX-S
(SC) 8 TX Unmanaged Fast Ethernet network switch for industrial networks with 8 copper ports and 2 optical fiber ports for single-mode optical fiber (100 Mbit/s)
B Network switch 2 FX-M
(SC) 8 TX MNG Managed Fast Ethernet network switch for industrial networks with 6 RJ45 copper ports and 2 optical fiber ports for multi-mode optical fiber (100 Mbit/s)
C Network switch 2 FX-S
(SC) 8 TX MNG Managed Fast Ethernet network switch for industrial networks with 6 RJ45 copper ports and 2 optical fiber ports for single-mode optical fiber (100 Mbit/s)
12 - Patch panel 0 None No patch panel
1 Patch panel 6 optical
fibers (SC/SC) Modular, flexible patch panel, terminals for 6 x SC adapter duplex
2 Patch panel 4 ETH Modular, flexible patch panel, terminals for 4 x RJ45 keystone pin connectors, shielded 3 Patch panel 8 ETH Modular, flexible patch panel, terminals for 8
x RJ45 keystone pin connectors, shielded
4 Patch panel 6 optical
fibers (SC/SC)/ 4 ETH Modular, flexible patch panel, terminals for 6 x SC adapter duplex, 4 x RJ45 keystone pin connectors, shielded
13 - Ethernet overvoltage
protection 0 None No surge arrester for Ethernet
1 2 2 x universal arrester for industrial Ethernet in
accordance with class E up to 250 MHz
2 4 4 x universal arrester for industrial Ethernet in
accordance with class E up to 250 MHz
3 6 6 x universal arrester for industrial Ethernet in
accordance with class E up to 250 MHz Code option Option
code Option Explanation
