Summary of Solar Application Scenarios Using In-package Hall-effect Current Sensors
Authors: Yang Wu, Bowen Ling, Harald Parzhuber, Steven Howard
Document ID: SBOA624
Publication Date: March 2025
Publisher: Texas Instruments
Abstract
Through-hole board mount hall-effect current sensors have been widely used in solar inverter systems for their convenient wiring and installation. However, open-loop versions often lack high accuracy over lifetime and temperature and are susceptible to damage during handling. In-package hall-effect current sensors, such as Texas Instruments' TMCS112x and TMCS113x portfolios, offer high accuracy with low drift, enabling precise current measurements across varying conditions. Their compact design reduces system complexity and cost without sacrificing isolation performance. Consequently, there is a growing trend to adopt in-package sensors in solar inverters to improve performance, power efficiency, and reliability.
1 Introduction
Accurate and reliable current measurement is critical for solar inverter systems, directly impacting power stage control and energy harvest efficiency. While traditional through-hole hall-effect sensors offer isolation and ease of installation, open-loop types often compromise accuracy over time and temperature. Close-loop sensors provide higher accuracy but are more complex, larger, and consume more power. In-package hall-effect sensors, like TI's TMCS112x and TMCS113x, present a superior alternative by combining high accuracy, low drift, and a compact design, thereby enhancing solar system performance, efficiency, and reliability.
2 Solar Application Scenarios with Hall-effect Current Sensing
Hall-effect current sensing is applied in various solar systems, including string inverters, residential inverters, hybrid inverters, micro inverters, solar power optimizers, and smart combiner boxes.
2.1 String Inverter
String inverters, typically three-phase with power levels exceeding 50KW, are used in commercial-industrial and utility systems. Hall-effect current sensors are employed for:
- String current sampling (for I-V curve scanning, diagnosis, and monitoring).
- Arc current detection (optional, for safety, complying with standards like UL 1699B).
- MPPT Boost current sampling (critical for MPPT accuracy).
- Three-phase current sampling (for inverter control, power generation statistics, and DC component suppression, adhering to standards like IEEE 1547-2018).
Diagram Description (Figure 2-1): This block diagram shows a 3-phase string inverter. PV arrays connect to MPPT modules. Each MPPT module has inputs for PV strings and outputs for boost current sampling. The inverter stage takes DC input and outputs 3-phase AC to the grid. Hall-effect current sensors are indicated for: 1. String current sampling, 2. Arc current detection (optional), 3. MPPT Boost current sampling, 4. Inverter 3-phase current sampling.
Diagram Description (Figure 2-2): This figure illustrates normal and abnormal I-V curves for PV systems, showing how current and voltage measurements are used for fault diagnosis. It highlights that accurate string current and voltage sampling is key to failure diagnosis accuracy and power generation efficiency.
Diagram Description (Figure 2-3): This diagram details the signal conditioning for 3-phase current sampling. The phase current is sensed, amplified, filtered, and buffered before reaching the DSP ADC for inverter control. A separate path, after filtering for DC component, is also sent to the DSP ADC for DC component suppression control.
Arc Current Detection: While current transformers (CTs) are common, in-package Hall-effect sensors offer a compact alternative for detecting arc currents (mA to Amperes, low to hundreds of KHz), which are crucial for preventing fires.
MPPT Boost Current Sampling: Accurate sampling of the average inductor current in the MPPT boost stage is vital for MPPT accuracy and overall power generation efficiency.
3-Phase Current Sampling: Essential for inverter power stage control, power generation statistics, and DC component suppression. High accuracy and low drift sensors help manage DC components within grid standards (e.g., <0.5% of rated current per IEEE 1547-2018). They also aid in accurate reactive power generation control.
2.2 Single-Phase Residential Inverter
Residential inverters (single-phase <10KW, 3-phase 10-50KW) have fewer MPPT inputs and PV strings per MPPT compared to string inverters. While string and MPPT boost current sampling requirements are less stringent, phase current sampling demands high accuracy similar to string inverters.
Diagram Description (Figure 2-4): This block diagram depicts a single-phase residential inverter. It shows PV strings connecting to MPPTs, a boost MPPT stage, and a DC-AC inverter outputting single-phase AC to the grid (L, N, PE). Hall-effect current sensors are indicated for: 1. Arc current detection (optional), 2. MPPT Boost current sampling, 3. Inverter phase current sampling.
2.3 3-Phase Hybrid Inverter
Hybrid inverters combine solar conversion with battery energy storage systems (BESS). They support multiple PV strings, DC-AC conversion, and DC-DC battery conversion. Power levels range from several KWs to tens of KWs. These systems require more current sensors due to BESS and off-grid Emergency Power Supply (EPS) functions. They may also support diesel generators.
- String current sampling.
- Arc current detection (optional).
- MPPT Boost current sampling.
- Inverter 3-phase current sampling.
- Bi-directional Converter (BDC) current sampling (for battery charging/discharging).
- Off-grid Emergency Power Supply (EPS) 3-phase current sampling.
- Neutral current sampling for midpoint potential balancing.
Diagram Description (Figure 2-5): This block diagram illustrates a 3-phase hybrid inverter. It includes PV strings connected to MPPTs, a DC-AC inverter, and a Battery Energy Storage System (ESS) with Bi-directional DC-DC Converters (BDCs). An AC relay connects to an Off-grid EPS. Hall-effect current sensors are marked for: 1. String current sampling, 2. Arc current detection (optional), 3. MPPT Boost current sampling, 4. Inverter 3-phase current sampling, 5. BDC Buck/Boost current sampling, 6. Off-grid EPS 3-phase current sampling, 7. Neutral current sampling for midpoint potential balancing.
BDC Current Sampling: Used for inductor current sampling in both high-voltage (non-isolated, 2-level Buck/Boost) and low-voltage (isolated topologies like DAB, CLLLC) battery charging/discharging circuits.
Off-Grid EPS 3-Phase Current Sampling: Used for backup power supply during grid outages. While not for power stage control, high accuracy is needed for metering and reliability.
Neutral Current Sampling for Midpoint Potential Balancing: Crucial for 3-phase systems with unbalanced loads. In hybrid inverters, a fourth leg (balancing bridge) actively controls midpoint voltage, requiring neutral current sampling. This compensates for voltage imbalances caused by uneven phase loads, preventing inverter shutdown.
Diagram Description (Figure 2-6): This diagram shows a conventional 2 split capacitor design for midpoint potential balancing in a 3-phase inverter. It depicts BUS +/-, two capacitors (C1, C2), and grid connections (L1, L2, L3, N, PE). The neutral point is between C1 and C2.
Diagram Description (Figure 2-7): This diagram illustrates a balancing bridge design for midpoint potential balancing in a 3-phase inverter. It features BUS +/-, capacitors (C1, C2), grid connections (L1, L2, L3, N, PE), and an additional fourth leg (balancing bridge). Hall-effect current sensors are indicated for: 1. Inverter 3-phase current sampling, 2. Neutral current sampling for midpoint potential balancing, 3. Balancing bridge, 4. EPS unbalanced loads.
2.4 Split-Phase Hybrid Inverter
Designed for markets like North America and Japan, split-phase hybrid inverters output split-phase power (e.g., 115V/230V). They also support unbalanced loads and integrate BESS and EPS functions, similar to 3-phase hybrid inverters.
- Arc current detection (optional).
- MPPT Boost current sampling.
- Inverter phase current sampling.
- BDC Buck/Boost current sampling.
- Off-grid EPS phase current sampling.
- Neutral current sampling for midpoint potential balancing.
Diagram Description (Figure 2-8): This block diagram shows a split-phase hybrid inverter. It includes PV strings, MPPTs, a HERIC inverter stage, ESS with BDCs, and an Off-grid EPS. Hall-effect current sensors are indicated for: 1. Arc current detection (optional), 2. MPPT Boost current sampling, 3. Inverter phase current sampling, 4. BDC Buck/Boost current sampling, 5. Off-grid EPS phase current sampling, 6. Neutral current sampling for midpoint potential balancing.
Diagram Description (Figure 2-9): This diagram illustrates a balancing bridge design for midpoint potential balancing in a split-phase inverter. It shows BUS +/-, capacitors (C1, C2), grid connections (L1, N, L3), and the balancing bridge. Hall-effect current sensors are indicated for: 1. Inverter split-phase current sampling, 2. Neutral current sampling for midpoint potential balancing, 3. Balancing bridge, 4. Split-phase unbalanced loads.
2.5 Micro Inverter
Micro inverters, typically rated from hundreds of watts to a few kilowatts, are used in residential settings, often for small rooftops or balconies. They can integrate BESS. In-package Hall-effect sensors help minimize PCB size and improve reliability.
- AC current sampling (for grid injection and power device protection).
- Resonant tank current sampling (for synchronous rectifier timing and overcurrent protection).
Diagram Description (Figure 2-10): This block diagram shows a micro inverter with two main sections: Totem Pole PFC/Inverter and Quad Boost DC/DC with CLLLC. Hall-effect current sensors are indicated for: 1. AC current sampling, 2. Resonant tank current sampling, 3. Resonant tank current sampling.
2.6 Solar Power Optimizer
Power optimizers work with string inverters to provide module-level monitoring, rapid shutdown, and MPPT. They use topologies like Buck or 4-switches Buck-Boost. For 4-switch Buck-Boost optimizers, in-package Hall-effect sensors are suitable for high-side inductor current sampling, especially given the high common-mode voltage (up to 150V).
Diagram Description (Figure 2-11): This block diagram shows a 4-switches Buck-Boost optimizer. It indicates the input from PV panels and a single Hall-effect current sensor for inductor current sampling, used for current loop control and protection.
2.7 Smart Combiner Box of Central Inverter
Smart Combiner Boxes (PV Stream Boxes) are used in large-scale PV systems between PV strings and central inverters. They reduce wiring, simplify maintenance, and enhance reliability. They typically support many channels (16-32) and sample all PV string currents. High accuracy is needed for failure diagnosis and power generation efficiency.
Diagram Description (Figure 2-12): This diagram illustrates a smart combiner box application. PV strings connect to one or more smart combiner boxes, which then communicate with a central inverter. Hall-effect current sensors are shown for: 1. String current sampling, used for current monitoring and communication.
2.8 Summary of Solar Inverter System and In-package Hall-effect Current Sensor
The following tables summarize key characteristics of different solar inverter systems and the typical usage of in-package Hall-effect current sensors.
Table 2-1. Summary of Solar Inverter System
| Solar Inverter System | String Inverter | Residential Inverter | Hybrid Inverter | Split-phase Hybrid Inverter | Micro Inverter |
|---|---|---|---|---|---|
| Phase type | 3-phase | 3-phase / 1-phase | 3-phase | 1-phase | 1-phase |
| Power level | Typ. 100 to 320KW | Typ. 5 to 50KW / Typ. 3 to 10KW | Typ. 5 to 25KW | Typ. 3 to 6KW | Typ. 0.5 to 5KW |
| Bus voltage | Typ. 1100V/1500V | Typ. 1100V / Typ. 600V | Typ. 1000V | Typ. 600V | Typ. 600V |
| No. of independent MPPT | K (Typ. 9/12/14/16) | K (Typ. 2/3/4) / K (Typ. 1/2/3) | K (Typ. 2/3/5) | K (Typ. 2) | K (Typ. 1) |
| No. of PV strings per MPPT | 2 | 2 / 1 | 2 / 1 | 1 | 1 |
| No. of total PV strings | J (Typ. 18/24/28/32) | J (Typ. 2/3/4/5/6/7/8) / J (Typ. 2/3) | J (Typ. 2/3/5) | J (Typ. 4) | J (Typ. 2) |
| No. of BDC | N/A | N/A | M (Typ. 2/3) | M (Typ. 1/2) | M (Typ. 1) |
| Neutral current sampling (Y/N) | No | No / No | Yes | Yes | No |
| Off-grid EPS (Y/N) | No | No | Yes | Yes | Yes |
Table 2-2. In-package Hall-effect Current Sensor Usage Statistics
| Where Used | String Inverter | Residential Inverter | Hybrid Inverter | Split-phase Hybrid Inverter | Micro Inverter |
|---|---|---|---|---|---|
| MPPT Boost current | K | K | K | K | K |
| String current | J-K | J-K | J-K | J-K | N/A |
| Inverter phase current (1) | 3 | 3 | 3 | 2 | 1 |
| Off-grid EPS current | N/A | N/A | 3 | 2 | N/A |
| BDC Buck/Boost current (2) | N/A | N/A | M | M | M |
| Neutral current | N/A | N/A | 1 | 1 | N/A |
| Total Quantities (3) | J+3 | J+3 | J+M+7 | J+M+5 | J+M+2 |
Note: 1. For inverter phase current sampling, whether in-package hall-effect current sensors can be used or not depends on the power level (current rating) of the inverter. In-package hall-effect current sensors can have thermal issues in high power inverters. 2. The table data is based on Buck/Boost BDC of inverter with high voltage battery. Isolated topology such as DAB and CLLLC, and so on of inverter with low voltage battery have more current sensors are not shown in this table. 3. Diesel generator and arc detection are optional functions, the corresponding current sensor quantities are not included in the total quantities. There has extra off-grid phase current sampling of the diesel generator port. The quantities for arc current sensors are equal to the number of total PV strings.
Table 2-3. Solar Inverter System Examples
| Solar Inverter Systems | String Inverter | Residential Inverter | Hybrid Inverter | Split-phase Hybrid Inverter | Micro Inverter |
|---|---|---|---|---|---|
| Phase type | 3-phase | 3-phase / 1-phase | 3-phase | 1-phase | 1-phase |
| Power level | 320KW | 25KW / 8KW | 20KW | 10KW | 5KW |
| Bus voltage | 1500V | 1100V / 600V | 1000V | 600V | 600V |
| No. of independent MPPT | K = 16 | K = 3 / K = 2 | K = 3 | K = 4 | K = 2 |
| No. of PV strings per MPPT | 2 | 2 / 2 | 2 / 1 | 1 | 1 |
| No. of total PV strings | J = 32 | J = 6 / J = 3 | J = 5 | J = 4 | J = 2 |
| No. of BDC | N/A | N/A | M = 3 | M = 2 | M = 1 |
| Neutral current sampling (Y/N) | No | No / No | Yes | Yes | No |
| Off-grid EPS (Y/N) | No | No | Yes | Yes | Yes |
Table 2-4. Examples of In-package Hall-effect Current Sensor Usage Statistics
| Where Used | String Inverter | Residential Inverter | Hybrid Inverter | Split-phase Hybrid Inverter | Micro Inverter |
|---|---|---|---|---|---|
| MPPT Boost current | K = 16 | K = 3 | K = 2 | K = 3 | K = 4 |
| String current | J-K = 16 | J-K = 3 | J-K = 1 | J-K = 2 | N/A |
| Inverter phase current | 3 | 3 | 3 | 2 | 1 |
| Off-grid EPS current | N/A | N/A | 3 | 2 | N/A |
| BDC Buck/Boost current | N/A | N/A | M = 3 | M = 2 | M = 1 |
| Neutral current | N/A | N/A | 1 | 1 | N/A |
| Total Quantities | J+3 = 35 | J+3 = 9 | J+M+7 = 15 | J+M+5 = 11 | J+M+2 = 5 |
3 Summary
With the continued investment and development of solar energy and ESS, more accurate and reliable current sensing technologies can make the grid safer and more efficient on energy harvest. In-package hall-based technologies such as TMCS112x and TMCS113x from Texas Instruments, can not only provide high accuracy combined with low drift, enabling accurate current measurements over both lifetime and temperature, but also have ease of use and low cost, which makes this popular to replace the traditional thorough-hole hall-effect current sensors. This application note summarizes common solar application scenarios where in-package hall-effect current sensors can be used. Read the following Design Considerations of In-package Hall-effect Current Sensor in Solar System, application note to learn more design challenges and how to solve those challenges.
4 References
- Texas Instruments, TMCS1126 Precision 500kHz Hall-Effect Current Sensor With Reinforced Isolation Working Voltage, Overcurrent Detection and Ambient Field Rejection, data sheet.
- Texas Instruments, Isolated Bidirectional DC/DC in Power Conversion System (PCS), application brief.
- Texas Instruments, Synchronous Rectification Control in CLLLC Converters Based on Hall-Effect Current Sensors, application brief.
- Texas Instruments, Design Considerations of In-package Hall-effect Current Sensor in Solar System, application note.
- Texas Instruments, Power Topology Considerations for Solar String Inverters and Energy Storage Systems, application note.
- IEEE, IEEE 1547-2018.
- PowMr, What is 100% or 110% unbalanced output inverter?, blog.
- Springer Nature Link, Power balance modulation strategy for hybrid cascaded H-bridge multi-level inverter.
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