Hệ Hybrid & InverterHybrid & inverter · BàiLesson 4/9
String Design for Hybrid Inverters
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Solar Knowledge HubThiết kế chuỗi pin cho biến tầnPV string design for the inverter
Bốn quy tắc chuyển thông số tấm pin và biến tần thành cấu hình lắp đặt cụ thể, ví dụ thực tế với Chisage ESS Eris 6,6kW (thông số đã đính chính theo datasheet).Four rules turn panel and inverter specs into a concrete layout, worked example with the Chisage ESS Eris 6.6kW (specs corrected from the datasheet).
Dải MPPT: ghi 60–425V, đúng là 150–425V. Điện áp khởi động: ghi 75V, đúng là 120V. Công suất tấm pin tối đa: ghi 10,56kWp, đúng là 9000W. Dòng đầu vào: ghi 18A, đúng là 17A. Dòng ngắn mạch: ghi 27A, đúng là 20A. Dùng số sai dẫn tới thiết kế chuỗi quá dòng hoặc biến tần không khởi động.MPPT range: stated 60–425V, correct is 150–425V. Startup: 75V → 120V. Max PV: 10.56kWp → 9000W. Input current: 18A → 17A. Short-circuit: 27A → 20A. Using wrong figures causes over-current string design or inverter fails to start.
| Tấm pinPanel | Tấm/chuỗiPanels/string | Vmp chuỗiString Vmp | Voc chuỗiString Voc | Tổng 2 chuỗi2-string total | Lưu ýNote |
|---|---|---|---|---|---|
| JA 640WJA 640W | 77 | ~310V~310V | ~370V~370V | 8,96kWp8.96kWp | ✓ Cân đối, dễ đi dây✓ Well-balanced, easy wiring |
| AIKO 655WAIKO 655W | 88 | ~364V~364V | ~436V~436V | 10,48kWp10.48kWp | ⚠ Vượt công suất tấm pin tối đa 9000W⚠ Exceeds max PV power 9000W |
| AE 730WAE 730W | 77 | ~292V~292V | ~347V~347V | 10,22kWp10.22kWp | ⚠ Dòng làm việc 17,51A vượt giới hạn 17A⚠ Operating current 17.51A exceeds 17A limit |
Vùng làm việc đẹp nhất của biến tần này là ~300–380V. Cả ba ví dụ nhắm vào vùng đó. Bài học lớn: phải kiểm tra cả dòng, không chỉ điện áp. Một chuỗi đạt điện áp nhưng vượt dòng đầu vào sẽ bị biến tần giới hạn, lãng phí công suất tấm pin dòng cao. Đó là lý do tấm dòng cao kén biến tần.This inverter's sweet spot is ~300–380V. All three examples target that range. Key lesson: always check current too, not just voltage. A string within voltage but over input-current limit gets throttled, wasting the high-current panel's power. That is why high-current panels are choosy about inverters.
Khi khách hỏi vì sao không nhồi thêm tấm cho nhiều điện hơn: số tấm mỗi chuỗi phải tính theo điện áp và dòng của biến tần, lắp quá sẽ vượt giới hạn và bị cắt công suất hoặc gây lỗi. Hệ thiết kế đúng chuỗi cho sản lượng ổn định và an toàn hơn hệ cố nhồi thêm tấm.When customers ask why they can't just add more panels: string count must be calculated from the inverter's voltage and current limits, exceeding them causes curtailment or faults. A correctly designed string yields stable output and safer operation than a crammed-in extra panel.
String design is the step that translates panel and inverter specifications into a concrete installation layout: determining how many panels go in each string and how many strings connect to each MPPT input. Done correctly, the system runs efficiently and safely; done incorrectly, the inverter may fail to start, undergo power derating, or sustain damage. This document walks through the process using a real-world example with the Chisage ESS Eris 6.6 kW inverter.
For: design and installation technicians, newcomers learning how to size strings, and sales staff who want to understand why panel count must be calculated rather than chosen arbitrarily.
Quick Summary
Four string design rules apply universally: the string operating voltage must fall within the MPPT range; the string open-circuit voltage must remain below the maximum DC voltage even in cold conditions; the string current must not exceed the maximum input current; and the total PV power must not exceed the maximum PV power rating.
For the Chisage Eris 6.6 kW, the correct datasheet values are: MPPT range 150 to 425 V, maximum DC voltage 500 V, startup voltage 120 V, maximum PV power 9000 W, two MPPT inputs, maximum input current 17 A per MPPT, and maximum short-circuit current 20 A per MPPT.
The optimal operating voltage window is approximately 300 to 380 V. Panel current deserves special attention: the AE 730 W panel, for example, has an operating current of 17.51 A, which already exceeds this inverter’s 17 A limit.
Four Rules and Inverter Specifications
Every string design follows the four rules introduced in document 04-03. To apply them, you first need the correct inverter specifications. For the Chisage ESS Eris 6.6 kW, the values from the official datasheet are as follows.
| Chisage Eris 6.6 kW Parameter | Correct Value |
|---|---|
| MPPT voltage range | 150 to 425 V |
| Maximum DC voltage | 500 V |
| Startup voltage | 120 V |
| Maximum PV power | 9000 W |
| Number of MPPT inputs | 2 |
| Maximum input current per MPPT | 17 A |
| Maximum short-circuit current per MPPT | 20 A |
The original infographic contained several incorrect Chisage specifications. The MPPT range was listed as 60 to 425 V (the correct value is 150 to 425 V). The startup voltage was listed as 75 V (the correct value is 120 V). The maximum PV power was listed as 10.56 kWp (the correct value is 9000 W). The input current was listed as 18 A (the correct value is 17 A). The short-circuit current was listed as 27 A (the correct value is 20 A). Using incorrect figures leads to over-current string designs or inverters that fail to start. All examples below use the correct values.
Three String Design Examples
The three panels from Chapter 02 are paired with the two MPPT inputs of the Chisage 6.6 kW, using datasheet specifications for each panel.
The JA 640 W panel has an operating voltage of 44.29 V and an open-circuit voltage of 52.87 V. Connecting 7 panels per string yields a string operating voltage of approximately 310 V (within the MPPT range) and a string open-circuit voltage of approximately 370 V, which is below 500 V and therefore safe. Two strings deliver a total of 8.96 kWp, giving a PV-to-inverter ratio of approximately 136%. The low current makes wiring straightforward.
The AIKO 655 W panel has an operating voltage of approximately 45.2 V and an open-circuit voltage of 54.50 V. Connecting 8 panels per string gives a string operating voltage of approximately 364 V and a string open-circuit voltage of approximately 436 V, still below 500 V. Two strings deliver a total of 10.48 kWp. Note that this figure exceeds the inverter’s maximum PV power of 9000 W, so this configuration is only appropriate if midday power clipping is acceptable; otherwise the number of panels should be reduced.
The AE 730 W panel has an operating voltage of 41.70 V, an open-circuit voltage of 49.50 V, and an operating current of 17.51 A. Connecting 7 panels yields a string operating voltage of approximately 292 V and a string open-circuit voltage of approximately 347 V, both within voltage limits. However, the operating current of 17.51 A exceeds the inverter’s maximum input current of 17 A, so the inverter will current-limit this configuration, making it non-optimal for this inverter.
| Panel | Panels per String | String Operating Voltage | String Open-Circuit Voltage | Total (Two Strings) | Notes |
|---|---|---|---|---|---|
| JA 640 W | 7 | approx. 310 V | approx. 370 V | 8.96 kWp | Well-balanced, easy to wire |
| AIKO 655 W | 8 | approx. 364 V | approx. 436 V | 10.48 kWp | Exceeds maximum PV power of 9000 W |
| AE 730 W | 7 | approx. 292 V | approx. 347 V | 10.22 kWp | Operating current 17.51 A exceeds 17 A limit |
The optimal operating voltage window for this inverter is approximately 300 to 380 V, the range where the inverter starts early in the day and sustains high efficiency. All three examples target this window. The key lesson from the AE 730 W example is that current must be checked, not just voltage. A string that meets voltage requirements but exceeds the maximum input current will be current-limited by the inverter, wasting the capacity of high-current panels. This is why high-current panels are selective about inverter compatibility.
Design Checklist
A concise set of practical thresholds for this inverter: string operating voltage should fall in the 300 to 380 V window; string open-circuit voltage must always remain below 500 V; panel current must not exceed 17 A per MPPT; and total PV power should be in the range of approximately 130 to 150% of inverter rated power, while not exceeding the inverter’s total 9000 W maximum PV power.
When a customer asks why they cannot simply add a few more panels to generate more energy, explain that the number of panels per string must be calculated from the inverter’s voltage and current limits. Exceeding those limits causes power clipping or faults. A system with a correctly designed string delivers stable, long-term output, far better than one where panels have been crammed in without proper sizing.
Chisage Eris 6.6 kW specifications cross-referenced against catalog V2.1.12 and datasheet Jup-3-10G2-LE: MPPT range 150 to 425 V, maximum DC voltage 500 V, startup voltage 120 V, maximum PV power 9000 W, maximum input current 17 A, maximum short-circuit current 20 A. Panel specifications for the three panels sourced from JA, AIKO, and AE datasheets as cited in Chapter 02. The AE 730 W current warning (17.51 A exceeding the 17 A limit) is based on direct comparison.